Most people who try infrared photography gravitate to the 720-nanometer IR filters, such as the Hoya R72. I thought I’d introduce you to some hard-core long-wavelength IR photography, using an 850nm filter. The long-wavelength part of the light spectrum has some costs associated with it. First, you lose the ability to make false-colors; you’ll have to stick to black-and-white. Secondly, you have to brace yourself (and your camera) for some really long exposure times (typically 2 or 3 minutes in sunshine). Black and white photos have a timeless quality to them that I have always loved. I don’t consider it a significant handicap to lose the ability to see colors in this range of the spectrum. People are encouraged to avoid landscape photography around mid-day, mainly due to the harsh shadows. The exact opposite rule applies to infrared; mid-day is the perfect time to be taking pictures. I find that overcast conditions or being under a tree canopy generally makes for drab and lifeless IR photos. Forget about portraits; hardly anybody could possibly hold still long enough (this doesn’t apply to IR-converted cameras, however). It could be fun on the beach, though, to magically make everybody disappear. Before I forget to mention it, these kinds of extreme exposure times will require you to cover up your viewfinder eyepiece. Such long exposures will let too much light leak inside your camera, so something similar to the Nikon DK-5 eyepiece cover or the eyepiece shutter (if your camera has one) is a requirement. Even well-built cameras leak a small amount of light through the eyepiece, but in most conditions it can be safely ignored. I have an 82mm diameter 850nm IR filter, and I use my set of step-up rings (with every size from 49mm through 82mm) to enable attaching it to nearly every lens I own. My filter is made by BCI, but several companies make them. I'm not overly impressed with the BCI filter quality, but their price was good. I would suggest you find another company's IR filters for shorter wavelengths; the BCI 720nm didn't cut off enough red light. You can’t see anything through the lens with the 850nm filter mounted, so you have to focus and compose first, and then attach the filter. Remember to either shift the focus according to the little IR focus dot on your lens (e.g. the really old Nikkor lenses), or else stop your lens down to at least f/8. Assuming you’d like to view a ‘neutral’ picture on your camera’s LCD screen, you need to come up with a preset white balance. Your camera won’t be able to automatically measure a white balance preset, and you can’t set a low-enough Kelvin temperature, either. I have an article here that might enable you to get an approximate preset, although it doesn’t work with all cameras. Please, please shoot in RAW format. This kind of photography is useless unless you do post-processing, and RAW formats will let you adjust your shot with the least collateral damage. If you’re unable to get a good white balance preset, RAW format will at least let you adjust the color balance in an editor after you take the shot. I will typically use noise reduction, alter highlights, shadows, increase contrast, convert to black-and-white, and also apply an un-sharp mask to each photo. You will need to make extensive use of your camera’s histogram feedback to arrive at the desired exposure. A typical exposure for this filter in mid-day sunshine is ISO 400, f/8 and 2 to 3 minutes. I set the camera on “time” exposure, which is only available in manual exposure mode on most cameras. Make sure you have plenty of battery power. Now, for the bad news. Most lenses are useless with infrared photography, even the expensive professional ones. The best lenses, in my experience, are the old manual-focus Nikkors; the ones that have the little red “infrared focus” dot on their focus scales. The lenses that don’t work for IR will get you a white blob in the middle of the photo. Surprisingly, a really good infrared-capable lens is the Nikkor (DX-only) 18-55 f/3.5-5.6 VR kit lens; infrared is the only thing I still use this lens for. Here’s a link to IR lens performance you will find handy (these guys also convert cameras into IR-only). The long infrared light waves have super penetrating power. As a result, sky and water gets incredibly dark. This filter reminds me of the old Kodak infrared black-and-white film photos. Your main enemy when shooting landscapes with this filter is wind. Every small branch and leaf will turn to mist. On the other hand, ocean and waterfall shots might just end up with a very nice effect. Examples Really dark skies and water, really long exposure. 18mm 154s f/10 ISO 400 You never know which plants will really glow in infrared Wind can be your enemy with the long exposure times The Light Spectrum Our extraordinarily limited view of the universe It’s amazing how little our eyes can see, compared to the range of light. Human vision stops at a little longer than 700nm, which explains the popularity of the 720nm filters (you get to see some IR, but exposure times are minimized). 850nm photography provides a glimpse into an otherwise-invisible realm. Light at this wavelength is so low in energy that it takes extremely long exposures to make our camera sensors sufficiently register it. The other end of the light spectrum, ultraviolet and beyond, is unavailable to photography unless you use quartz lenses. Normal lens glass is opaque to ultraviolet. These UV lenses are rare and expensive. Contrary to what you might think, a UV filter blocks UV light and is the opposite of what you need for this kind of photography. Did you know that bees can see in ultraviolet? Conclusion The 850nm filter gets you a kind of “moonlight” effect. The sky loses the tobacco-color you get from shorter-wavelength IR filters, and your shots all tend to look like they were taken at night. Think of 720nm filters as “daytime” IR, and 850nm as “nighttime” IR. You probably won’t want a steady diet of this kind of photography, but if you want dramatic landscapes, this filter delivers. You will see the world in a whole new light. #review

No, you can’t simulate the fast-focus or weather-sealing of the pricey big glass. But you can simulate the ‘look’ of those expensive telephotos with a modestly-priced telephoto lens. The reason big telephotos have their signature ‘look’ is largely their de-focused backgrounds. The subject is the only thing in focus, and everything else just melts away when those lenses are shot wide-open. You still need a lens that has the reach of big telephotos, but you can easily de-focus the backgrounds with software. The best way to do this is with a mask. What you need is a program that lets you select the background, and then use Gaussian blur to make that background melt away. Keep in mind that sometimes you stop down a lens because you want the extra lens resolution it gets you, but you pay the price by ruining the background. It’s totally amateur to let power lines and chain-link fences remain visible in the background. If you blur the background after the fact using a photo editor, you can get the best of both worlds. That annoying background clutter can magically disappear. There’s another problem that many photographers often encounter. If you’re at a zoo that uses mesh or bars around their enclosures, you’ll discover that the backgrounds of your photos have a nasty repeating pattern to them, even though the subject is sharp and the backgrounds are (mostly) out of focus. This is what’s known as ugly bokeh, although this kind it isn’t caused by your lens optical design. Maybe you can’t see the mesh itself, but its effect is still felt. Your first inclination is probably to either reject the photo or try to use a healing brush to fix the background. Wrong on both counts. Healing brush tools are very labor-intensive, and often involve a considerable amount of skill to use them well. You can usually get rid of irritating background details with considerably less effort via the “Gaussian blur” effect instead. Many editing programs offer masking features, and nearly all of those same programs offer the Gaussian blur effect. I used to think that the last thing I wanted was to blur my photos; it didn’t occur to me that Gaussian blur is virtually never used outside of a masking operation (they’re not applied “globally”). Big, expensive, 600mm f/4 lens “look” The shot above doesn’t have any obtrusive background detail to spoil the scene, but that’s not how the original shot looked. I wanted the two tiger faces to be in focus, but they weren’t both at the same distance. I stopped the lens down a bit to get sufficient depth of focus, but that also caused the ugly background to just look worse and worse. The cold cruel reality of the original shot I knew when I took the shot that it could be improved in an editor, but I have to admit that I wasn’t sure if it could be turned into a ‘keeper’. You don’t always get to maneuver into a position where you can control both the main subject and the background, although you should always strive to do so. The mask used with Gaussian Blur (from Capture NX2) Personally, I don’t like to completely obliterate the background into a featureless single color. I like what I call a watercolor effect, where the background is blurred, but the environment still shows through a little bit. The beauty of the Gaussian blur is that you get to choose how much to use via the selected ‘radius’ and opacity. Image editor masking tools allow both adding and erasing of the mask, so you needn’t be worried about being extra careful as you mask. Just erase your mistakes and try again. I’m a Capture NX2 holdout, but most image editors offer similar masking options. The Gaussian blur technique is just one more option that’s available for use in your photography. I think that too often it’s an overlooked tool. You might just find that you can salvage shots that you originally thought were worthless. And it’s not even that much extra effort. #howto

One of my goals while comparing different infrared lens filters was to perform resolution testing, to get actual MTF50 numbers. People often hand-wave about infrared filters ruining the photo resolution, but they have no numbers to back their claims up. Theoretically, infrared photography should have lower resolution due to its longer-than-visible wavelength of light. Camera sensors mainly respond to the IR light as ‘red’, which is only a fourth of the sensor Bayer “RGGB” pixel population, so that should also lower the resolution. Cameras with opaque IR filters mounted on their lenses can’t auto-focus, either. You need to focus and compose the shot without the IR filter attached, and then add the filter to take the shot. If you’re lucky, your lens has an IR focus-compensation mark on its focus scale to help you manually shift the focus before taking the shot. I’m not going to discuss cameras that have been permanently modified to shoot infrared. I’m only talking about mounting different infrared filters onto off-the-shelf digital cameras. With these three strikes against it, infrared photography is bound to suffer from lower resolution. But how bad is it? I set up my large (size A0) resolution chart to find out. I chose my ancient Nikkor 105mm f/2.5 pre-AI lens for testing, because it’s as good as I have for handling IR light, and the longer focal length is ideal. Wide-angle lenses are poor subjects for resolution testing, because the required close distance from the chart leads to unrealistic testing. This old 105mm lens can’t be mounted on new cameras that have a “meter-coupling lever” used for setting apertures. For this reason, I used a Nikon D5000 that doesn’t have one of these levers on it. I can’t buy a Nikon kit for this lens to upgrade it to “AI”, which I have done for my Nikkor 20mm f/4 lens, for instance. After photographing my resolution chart, I discovered that the chart fiducial targets (mainly little black squares) are either semi-transparent or fully transparent to infrared! Shorter IR wavelength filters produced medium-grey target photos, and longer IR wavelength filters made the targets completely invisible! What to do? My resolution charts are printed from a high-end, large-format inkjet printer that uses dye-based inks. It never occurred to me that IR light would penetrate right through these chemicals. Doh. I tried printing a focus chart (11” X 17”) using a laser printer next, since those prints are based on toner particles instead of dyes. I don’t have access to laser printers that print larger than 11X17, but I figured I could still get reasonable measurement numbers from my analysis software. The laser printer black toner powder contains “carbon black”, which still looks black in infrared light. The laser print quality isn’t as good as my high-end inkjet chart, but at least my camera can now see the chart. My next problem was focus. Even using the focus-compensation mark on my lens, the resolution chart photos looked pretty soft. I couldn’t tell if this softness was due to poor focus or the IR filter effects. Maybe both. My analysis software (MTFMapper) also has the ability to evaluate focus, using a separate “focus” chart that is rotated at 45 degrees about the vertical. This focus chart also has little squares (or trapezoids) that can have their edges measured for resolution. I decided to perform my analysis using the focus chart instead of the resolution chart, since I could tell where sharpest focus was, and I could still get some resolution measurements. These resolution measurements are only at a few chart locations, instead of across the whole camera sensor that the resolution targets provide. I figured that this was a reasonable tradeoff. This technique made my tests insensitive to the inevitable focus errors. I tested three different IR filters. The first is the Hoya R72, which is tuned to 720 nanometer light (short-wave IR). The second filter is the Neewer 850nm, which I estimate to be more like 740nm instead of 850nm. I don’t have the necessary instrumentation to measure spectral response, so this is just a guess. The third filter is the BCI 850nm (long-wave IR). Update 8-14-2018 I added the Zomei 850nm filter to the testing. It appears that its spectral response matches the BCI 850nm filter. I believe that the Zomei 850nm is superior to the BCI 850nm in how even the lighting is across the whole filter. The BCI has a slight light-dark variation that looks like concentric rings; the Zomei is completely even. The focus chart design, showing where the lens should be focused The picture above shows what the focus chart looks like. The left-hand side of the chart is rotated away from the camera by 45 degrees about the chart center vertical axis. You focus on the right-hand edge of the large middle rectangle (as shown above in red), and you expect that the nearest and farthest little black squares will be out of focus. Focus Chart, No IR filter, NEF format The focus chart detail shown above, using an un-sharpened RAW format photo, shows the measurement results without any filter. The manual-focus lens has peak resolution measurements of 0.19 cycles per pixel, or an MTF50 of 39.8 lp/mm. The plane of best focus is a little in front of the large focus-target rectangle. The baseline for this lens is therefore 0.19 c/p resolution for un-sharpened raw photos at this aperture. The lens was re-focused after taking the above “no filter” shot, to compensate for the IR focus shift. I used the IR focus-shift dot on the focusing scale to manually shift focus, which I then left alone for all subsequent shots with the various IR filters. Nikon hasn’t said what frequency of IR light that this dot is calibrated against (but I bet it’s for short-wave IR). Infrared focus dot sample. Shift focus by this amount. Different manufacturers will designate the infrared focus shift with different marks (if they bother to do it at all). Some marks look like little diamonds instead of circles. Focus Chart Detail, Hoya R72 IR filter, NEF format The lens has peak resolution measurements of 0.13 cycles per pixel using the Hoya R72 filter, or an MTF50 lp/mm of 27.2. The plane of best focus is right at the leading edge of the large rectangle, where it should be. The resolution has taken quite a dip, going from 39.8 (no filter) to 27.2 lp/mm (Hoya R72). Without changing focus, I then switched to the Neewer 850nm filter. Focus Chart Detail, Neewer 850 nm IR filter, NEF format The Neewer 850nm filter is measuring 0.13 c/p, which is the same resolution as the Hoya R72 filter (MTF50 lp/mm of 27.2). Notice, though, that the plane of focus has shifted farther away from the camera and away from the target rectangle leading edge. Because this filter is about a stop slower than the Hoya R72, I assume the Neewer 850 is blocking the shorter, more energetic IR wavelengths compared to the Hoya R72. The longer wavelengths aren’t focused as well with this lens, and therefore the plane of focus is shifted farther from the camera. I really don’t believe that this Neewer 850 filter blocks wavelengths up through 850nm, though, based upon my other IR filter (BCI) which claims to be an 850nm filter as well. Focus Chart Detail, BCI 850nm IR filter, TIF format My MTFMapper software couldn’t analyze the raw-format shots from my BCI 850nm filter. If I converted the photos into TIF, however, the software could analyze them. The focus plane has alarmingly shifted much farther from the camera, with the longer-wave IR light. The lens just can’t bend this IR light enough, so the focus shifts more and more as wavelength increases. The Nikon IR focus-shift dot is definitely not sufficient to work for this filter. Since I had to convert the photo into TIF format for the sake of the software, it got some undesired extra sharpening by the conversion software. As a result, the resolution peak measurements of 0.17 c/p are bogus. I know that my photos that are converted into other non-raw-formats (jpeg or tif) measure artificially higher resolution. Focus Chart Detail, BCI 850nm IR filter, NEF format, New Threshold Update 8-14-2018 I discovered I could lower the MTFMapper software threshold setting, and it could then analyze the raw-format photo. The resolution of 0.13 c/p matches the other IR filters (Hoya and Neewer). Focus Chart Detail, Zomei 850nm IR Filter, raw format I recently got another filter to analyze: Zomei 850nm. This filter looks very similar to the BCI 850nm filter. The resolution peak of 0.12 c/p is basically the same as other filters, given the measurement tolerances can easily vary by 0.01 c/p. In this photo, I shifted the IR focus compensation by double the amount of the IR mark on the lens. The focus compensation still needs a small amount of additional closer-focus than I gave it. Conclusion As expected, all of the IR filters I analyzed decrease lens resolution quite a bit (at least 30%). All of the tested filters essentially match each other with their impact on lens resolution. I was surprised to see that the really inexpensive Neewer 850nm has the same resolution as the Hoya R72; I would have expected it to be worse. What was really unexpected, however, was the large variation in focus shift according to the wavelength of the IR filters. The infrared focus-shift marks on lenses are very approximate at best. The only consistent theme seems to be that you need to focus closer with infrared compared to visible light. You should stop down the aperture to avoid ruined shots due to the lens being out of focus. If you do much shooting with a long-wavelength IR filter, I’d recommend that you make your own custom mark on your lens for the correct focus shift. Stopping down the lens may be sufficient to hide the focus shift, if your lens is a wide angle. Beware of stopping down your aperture too much; IR hot spots or concentric rings might start to appear. The BCI 850 filter, which is dimmer than the Neewer 850 filter by about 3 more stops, causes a huge focus shift. I believe this is because the BCI filter only passes longer IR wavelengths, which the lens can’t focus (bend light rays) as effectively. The BCI 850 is only useful for black and white, because the color information at these wavelengths is mostly eliminated. #howto

Why are photographers interested in infrared photography? I think it mostly boils down to getting an interesting ‘look’. They want to see plants glow, as if they’re covered in heavy frost (it’s called the Wood Effect, after the photographer Robert W. Wood who discovered this in 1910). They also like to see really dark skies and have the magical ability to make atmospheric haze virtually disappear. Freckles can be made to vanish. There are probably a few photographers that are curious to find out if swimming suits really do disappear in IR light. I’m not willing to sacrifice one of my cameras to get converted into full-time infrared. I’m going to stick with using IR filters instead. I do have to pay the price of really long exposures, which means manual focus and framing before attaching the filter, and it additionally means I need to use the Nikon DK-5 eyepiece cover to stop eyepiece-entering light from ruining my shots. Do I also have to pay a high financial price for a high-end IR filter to get decent IR photographs? Will bargain filters work okay? Some tests are in order. I doubt most photographers really care exactly which percent of different light frequencies are involved. Enter cheap IR filters. There’s an explosion of cheap IR filters available, and I couldn’t resist trying a few of them. I soon found out that light frequency transmission standards are pretty much nonexistent when it comes to many IR filter producers. In other words, 720nm and 850nm could be replaced with “fat free” and “non-gmo” with equal accuracy. On the other hand, what I surprisingly didn’t find were optical aberrations, bad threads, or plastics in the filters I tried. I’m sure these kinds of problems can be found in cheap filters, but I guess I got lucky. I wouldn’t touch a plastic filter, no matter how cheap it is. I ended up testing IR filters from Hoya, BCI, Neewer, and Zomei. All of these filters use optical glass and have metal mounts. I haven’t seen any significant differences in optical resolution or thread quality with any of these filters. As previously mentioned, the main differences I observed have to do with light spectral response. I avoid pointing the lens at light sources when shooting IR; I don’t think multi-coating is much of a consideration with infrared filters (the lenses themselves struggle with significant internal IR reflections). I did find a problem unique to the BCI 850nm filter; it had uneven optical density across the field of view. The filter produced what looked like a series of light-dark concentric circles, centered about the middle of the field of view. It was easy enough to hide these circles using an image editor, because the light-dark pattern wasn’t too severe. Still, I’d avoid recommending the BCI 850 filter because of this defect. I seem to keep returning to my ancient manual-focus Nikkor prime lenses for infrared photography. These old lenses have the best internal absorption coatings for the (entire) tested infrared region of the spectrum, they have great manual focus scales, and they also have the little infrared focus-shift reference ‘dot’ on them. Exposure and focus is manual anyway, so these old lenses don’t present any disadvantages. Unfortunately, I can’t mount any of the old Nikkor lenses unless they’ve been converted to “AI”, in order that I don’t damage the meter coupling tab (on most of my cameras). My old Nikon D5000 and D60, by the way, don’t have a meter coupling tab on them. This means that I can use the old non-AI Nikkors on them without any problem. Many lenses will work acceptably for infrared at wide apertures, but they start to develop the nasty white hotspot at f/8 or narrower apertures. The hot spots tend to get worse as you use the longer-wavelength filters. Keep checking this link for updates to lenses (from all lens manufacturers) that are suitable for infrared photography here. I always have to mention my Nikkor 18-55 DX f/3.5 – 5.6 VR lens. It’s IR performance is very good. Manual focus is a pain with it, however, and it’s not FX. After I did some testing to determine how much to compensate for the infrared focus shift, I discovered that the little Nikon IR focus scale compensation dot is calibrated for roughly 720nm light. You need to shift focus about twice this amount when using 850nm filters. I put a little dot of white fingernail polish on my manual Nikkor lenses to indicate the 850nm focus shift. My favorite camera for infrared use is my Nikon D610. Infrared exposure times get really long, so I like to crank up the ISO to minimize those times (up to ISO 2500). The D610 sensor is very forgiving with high ISO’s; for other cameras, I lower the ISO and live with longer exposure times. I have to switch to “Bulb” or "--" (time exposure) and use a remote release for exposures longer than 30 seconds (click to raise the mirror, click to start exposure, click to end exposure). Hoya R72 Infrared Filter This is a fairly well-regarded filter and lens company. The R72 purportedly cuts off light wavelengths shorter than 720 nanometers (actually meaning less than 50% transmittance of visible light below 720nm). It has good mechanical and optical quality. This filter isn’t inexpensive; I doubt that many people could call it inferior in any way. I have no way to measure spectral response, but I believe the Hoya light response claims to be true (see the chart below). The sky ends up being reasonably dark, and green plants have their characteristic glow. You can’t see anything when you look through the filter (human vision ranges from 390 to 700nm). I’m unable to measure a white balance to get a preset with my cameras when I use this filter, since these modern cameras are a bit too efficient at filtering out IR light. (My old Nikon D50 and D60 could get a white balance preset with the Hoya R72). I can get a decent preset white balance by ‘borrowing’ the white balance from my Neewer 850nm filter (see below). My main complaint with this Hoya filter is that colors (after getting a neutral white balance) are a little bland. Cranking up the color saturation in post-processing only adds a marginal improvement. The medium-dark sky yields a “tobacco” color after the photographs get a proper white balance. In some circumstances, the ‘look’ of this filter is what I want, but not always. Hoya R72 filter specifications, courtesy Hoya Optical The graph above shows why you can’t see through this filter (it only transmits above 700nm). Pure infrared light, even at the lower wavelengths, has very little of what we can perceive as “color”. The lack of a broader spectrum of low-wavelength light translates into dull colors. You can convert the pictures into black and white, if the weak colors don’t tickle your fancy. Typical Hoya R72 shot with neutral white balance Note in the shot above that some of the cactus plants become translucent in infrared light. There are nearly always some visual surprises that you’ll see after a day of shooting IR. Typical Hoya R72 shot with hue shift for the “blue sky” effect I have been perfectly content with the ‘look’ of the Hoya R72 for several years, but I think my tastes are starting to change. Can I get a better ‘glow’ from other filters? Are the colors the same with other wavelengths? Read on. Bear Claw Industries (BCI) Infrared 590nm, 665nm, 720nm, 850nm These filters are inexpensive, so I figured it would be a low-risk experiment to try them. I got the 82mm thread size, and I use step-up rings to fit my different lenses. The filters came as a kit; normally I would avoid ‘IR’ filters with wavelength cutoffs below 700nm. I have no complaints about the quality of the optical glass or metal threads on these filters. But… I knew there was going to be some trouble when I opened up the box and could see right through three out of four of these filters. You’d think that the BCI 720nm filter would look just like the Hoya R72; not even close. The “infrared” 590, 665, and 720nm filters visually all look like shades of red/orange; this would be expected for the 590 and 665 filters. Orange is 590nm to 620nm, and red is 620nm to about 750nm, according to Wikipedia, although it also says you can’t see beyond 700nm. Hmm… Methinks BCI must be stretching the truth a bit with their 720nm filter. I couldn’t see any “Wood Effect” whatsoever with photos taken through the 590, 665, and 720nm filters. I just can’t detect any infrared effect. The BCI 590, 665, and 720 nm “infrared” filters are a bust. I can’t comment on how these filters would perform on an infrared-converted camera, but their filter labels of “Infrared” seem to be false advertising. The BCI 850nm filter, however, is opaque to human vision. Shots through this filter show up as deep purple, unless you configure a proper camera white balance first. Light transmission is about 4 stops lower than the Hoya R72, so exposures are pretty long. I really, really like the lighting effect with the BCI 850, although the pictures need to be converted into pure black and white. There isn’t anything you’d call ‘color’ with this filter, so infrared color photography isn’t an option. The sky is rendered super dark, and plant chlorophyll really glows. The bad news, though, is that many of my lenses that seemed fine with the 720nm IR spectrum start getting nasty internal reflections at 850nm. Exposure times are quite long with this filter, typically extending to a few minutes. I don’t dare use really wide apertures with this filter, because the infrared focus shift typically leaves you with out-of-focus shots. My Nikkor 18-55mm VR “kit” lens, which is normally very good at infrared, started to show slight internal reflections at f/11, which only got worse at smaller apertures. These longer 850nm wavelengths work well with very few lenses, compared to the 720nm wavelength filters. I am completely unable to get a white balance measurement with this filter. Fortunately, I can ‘borrow’ a very usable white balance preset from my Neewer 850nm filter (see below). It still requires conversion into black and white, but at least the camera LCD shows a decent neutral-balanced picture (with a faint blue color cast). BCI 850nm long-wavelength loses color information The shot above is typical of the character of light transmitted by the BCI 850nm. The original shot was converted into black and white, to rid the slight color cast. Photos without a preset white balance will look deep purple. This filter is excellent for eliminating atmospheric haze. You lose the “distance” cues in landscapes, since the gradual increase of atmospheric haze is absent. Be prepared for very long exposure times. You might find this filter handy as a super-neutral-density filter, although only for black and white. My big complaint with this filter, as I alluded to above, is uneven light transmission across the field of view. The sky can look like it has a monochrome rainbow in it, depending upon the lighting conditions and direction. I can fix this defect in my editing software, but this is the fatal flaw in my BCI 850. Neewer 850nm Infrared Filter Here’s where I got a very pleasant surprise. I was expecting this filter to match the results of the deep-infrared BCI 850nm and Zomei 850nm filters. Not even close. The nearest visual equivalent to this Neewer850 would be the Hoya R72, but the colors are quite different (much more saturated). I’m guessing that it should probably be labelled something like “Neewer 700nm Infrared”. This filter is really dirt cheap, and I like the lighting effect it achieves. I have no complaints about the Neewer filter threads, and I haven’t noticed any optical imperfections, either. It does seem that there is a gradual vignetting toward the edges of this filter, which generally adds to more dramatic skies. The Neewer850 is visually opaque, but the color results are wild. I’m actually able to get a successful camera white balance measurement with all of my cameras when using this filter! I usually point my camera at green lawn grass to get the white balance preset measurement. My camera histograms show a healthy amount of red, green, and blue in them, which might be why the white balance measurement succeeds. The exposure is about a stop slower than the Hoya R72, and about 3 stops faster than the BCI850/Zomei850. A typical sunshine exposure is ISO 400, f/8, and 30 seconds for this Neewer850. I like to keep exposure times at 30 seconds or less, since otherwise you need to deal with the hassle of externally-timed exposures. I avoid apertures wider than f/8, due to the uncertainty of focus. Exposures are all over the map with infrared, so you will have to rely heavily on your camera histogram feedback. I really like the colors as-shot with my measured IR white balance preset from lawn grass. The sky is a great red-orange, compared to the drab tobacco color result from the Hoya R72. If I want to create the in-vogue “blue sky” color infrared shots, I prefer to use the Viveza 2 plug-in (via Lightroom) and perform a hue shift of roughly -150. This provides essentially the same effect as the “red-blue channel swap” popular with Photoshop. This hue shift only works if the photo has a proper neutral white balance to begin with. Depending upon the photo, sometimes the effects from processing the shot in the HDR Efex Pro 2 plug-in (via Lightroom) can be really pleasing. Neewer 850nm, as shot. Nikkor 20mm f/4 at f/8, Nikon D610 The shot above shows the colors I get when the camera uses a white balance obtained from green lawn grass. The orange sky looks much more vivid than the Hoya R72 tobacco color. Foliage has the nice Wood Effect ‘glow’, as well. Note the gradual vignetting of the sky. Neewer 850nm, hue shift, via the Viveza 2 plug-in in Lightroom The sky shown above looks more saturated and dramatic than the typical Hoya R72 filter photo. Vegetation takes on the characteristic yellow color. This hue shift is equivalent to the red-blue color channel swap in Photoshop, but Viveza 2 gives much more control over the channel mixing. Addition of extra warmth in post-processing after the hue shift would benefit shots like this. Neewer 850nm after HDR Efex Pro and Viveza 2 In the shot above, I first used the HDR Efex Pro plug-in via Lightroom. I started with the original neutral white balance shot, but turned it into HDR to get more dramatic lighting and saturation. Next, I took the single-shot HDR and then performed a hue shift inside Viveza 2 to transform the orange/red colors into magenta. You wouldn’t want a steady diet of this stuff, but the effects that can be obtained from the Neewer 850nm filter combined with HDR Efex Pro and Viveza 2 can be very dramatic. If you want your photos to stand out from the crowd, here’s one way to do it. Zomei 850nm Infrared Filter This filter produces visual results that look almost exactly like the BCI850. Unlike that BCI850, however, this filter produces perfectly even light transmission across the field of view. This Zomei is becoming my go-to filter for super dramatic pure black-and-white IR photography. The exposure times nearly match the BCI850 filter. They’re about 4 stops slower than the Hoya R72. My camera histograms, when using the preset white balance I borrowed from using my Neewer 850nm filter, typically show a perfectly even balance of red, green, and blue. It’s as if I used a grey card to calibrate this filter. The Hoya R72, for comparison, shows about 80% of the histogram as a red channel response. As I mentioned earlier, I cannot get a direct preset white balance measurement using this filter, so I just borrowed the white balance from the Neewer 850 filter. If I could only keep a single IR filter out of my collection, this would probably be the one. My only complaint is the long exposure times. Zomei 850nm, toward the sun Shooting in the direction of the sun leaves the sky dark, but not nearly as dramatic when compared to shots with the sun behind your back. Neewer 850 comparison shot It's astonishing to think that the Neewer 850 shot above has the same specifications as the Zomei 850nm shot. They couldn't be more different! Zomei 850 away from sun The sky has really turned dark with the sun behind me. When you're shooting dry vegetation and rock, the subjects look about the same as regular black and white. Plants with chlorophyll, however, turn almost pure white. Conclusion Compared to cameras and lenses, trying out some cheap IR filters carries a very low financial risk. Don’t expect scientifically accurate results from these filters, however. If you get nasty hot spots in the middle of your photos, don’t blame the filter; blame the lens. You’ll need to experiment with focus compensation, depending upon which filter is being used (longer wavelengths require focusing much nearer). Please, please remember to cover your camera eyepiece to avoid washed-out pictures (such as the Nikon DK-5) or else use the built-in eyepiece shutter on the more ‘pro’ camera models. Always take the photos using Raw format, to give yourself sufficient elbow room when you process the shots in your editor. These kinds of filter experiments can open up a whole new photographic area to explore. There are more and more companies starting to offer IR filters, so go try some of them! Avoid any plastic filters, however. The range of visual effects that you can achieve with different IR filters is really amazing. If you have an adventurous photographic spirit, this is a great avenue to explore without having to make a significant investment. There’s a kind of dreamy charm that is unique to IR photography. And no, I don’t know if any of these filters make swimsuits transparent. Those tests will have to wait for another day;) Also, I’ll bet that swimsuit manufacturers got wise to IR photographers a long time ago and switched to opaque fabrics. #review

This lens is a blast from the past. The lens was introduced in 1991, and (if what I’ve read is correct) is the very first 24-70 zoom lens. It was developed during ‘film’ days, so of course it’s full-frame. Back then, this zoom range was considered a bit odd, but it’s now probably the most common zoom range used by professional photographers. Tamron made this lens for Nikon, Canon, and Minolta (remember those guys?). I’m just reviewing the Nikon mount, but the optics aren’t any different for the other mounts. As the title suggests, it’s a variable-aperture zoom. This lens has a funky very thick rubberized zoom and manual focus ring. After having thought more about it, however, it’s a very sensible design idea. Your gear WILL get knocked around, and having a thick rubber bumper around it might just save it someday. The zoom ring is nearest the camera body; it’s very grip-able and plenty wide enough. Not many lenses had an aspherical lens element when this lens came out, so Tamron marketers really played it up. They needed aspherics to achieve the zoom range on the short end (28mm was the typical barrier at that time). They succeeded in this goal; the lens works best at 24mm, as a matter of fact. What you won’t notice with this lens is any objectionable distortion. It’s quite impressive for a lens this old to not see the typical heavy barrel distortion. The lens extends maybe a half inch when you zoom it to 70mm, so it stays short. Being a screw-drive lens, you can’t just alter focus by twisting the focus ring; you need to place the camera body into manual-focus mode first. I discovered that it works well for infrared photography. Most lenses leave a white hotspot in the middle of your IR pictures, but not this one. Here’s a link to common lenses (all camera brands) that have been evaluated for their utility with infrared. Its IR capability is the reason that I keep this lens around. I just wish the lens had a focus scale, since IR photography requires a focus shift. The biggest complaints from users of this lens include noisy focus and poor contrast at some aperture/focal length combinations (mid-frame weakness). The lens also has a rotating front element, which really annoys people that use polarizers. My own biggest complaint might be the corner sharpness, having gotten used to the Nikkor 24-70 stellar performance. The bokeh isn’t the greatest, either. I find it hard to get over how much smaller this lens is when compared to the Nikkor 24-70 f/2.8 E VR. Not that I consider the Tammy to be competitive; the Nikkor smokes it in every way optically (except for infrared photography). The Nikkor doesn’t smoke this lens in price, however; you can pick one up for dirt cheap on E-bay, but the same can’t be said for the Nikkor. It’s only 9.7 ounces and 3 inches long, compared to 38.4 ounces and 6 inches long for the Nikkor! I remember a long hike in the desert where I definitely would have swapped that Nikkor for this Tammy. It has a filter thread of 62mm. It comes with a ‘tiny’ bayonet-style lens hood that’s only about a half inch long; there’s really no reason to remove it unless you’re changing filters. This lens is the old-style “screw drive” auto-focus, compared to the modern AF-S lenses with an internal silent-wave motor, so it won’t work on lesser Nikon camera models. Speaking of focus, the Tammy focuses down to 15.7 inches, which is about the same as the 24-70 Nikkor. I noticed while performing focus calibration testing on my D610 that the 24mm fine-tune value (10) was about 2 counts different from the 70mm fine-tune value (8). Interestingly, I noted the same thing when I calibrated the Nikkor 24-70 lens. I wish all manufacturers used the Sigma USB dock technology to allow custom calibration at different focal lengths and focus distances. I heard as of this writing that Tamron, in fact, does provide a USB “TAP-in Console” for their newest lenses for calibration similar to Sigma! Resolution Tests As the following measurements will show, this lens struggles in mid-frame at all focal lengths. If you’re willing to stop down to f/8, you can get good results from 24mm through 50mm and generally even better at f/11. At 70mm, you need to stop down to about f/11 for good resolution across the frame. Don’t shoot with this lens wide open. Period. You have been warned. You can get by at f/4 from 24mm through about 28mm, but lens performance is vastly improved by f/5.6. The sweet spot is generally f/8.0, which should surprise nobody. This lens is much better at short focal lengths, particularly at 24mm. The EXIF data identifies 24mm as 25mm. At any focal length, the meridional-direction resolution is pretty bad. The substantial difference between meridional and sagittal directions spells significant astigmatism. I used the Nikon D610 FX for testing. 24-70 Tammy on Nikon D610. Funky rubberized zoom & focus rings. This is why you were warned to never shoot this lens wide open. Terrible corners and pretty heavy vignetting wide open 24mm Better, but not good at 24mm f/4.0 Pretty useful at f/5.6 Much better at f/8. Note characteristic weak mid-frame performance Corners are pretty good now, but the meridional remains weak Pretty sad meridional performance leads to substantial astigmatism Strong performance at 24mm, f/11 in sagittal direction Diffraction setting in by f/16. It’s much worse at f/22 38mm f/8 Not as good as 24mm. Pronounced mid-frame weakness. 48mm f/8 Better than 38mm, but 24mm is still better Up through about 50mm, the lens makes a good showing of itself by f/8. When zooming out to 70mm, the lens performance gets weaker. Let’s look at the whole f-stop range (except f/22) at 70mm next. 70mm wide open at f/5.6 is downright embarrassing 70mm f/8 still isn’t acceptable 70mm f/11 Center is fine, but nowhere else 70mm f/16 sagittal is fine, but meridional edges aren’t acceptable Samples 850nm Infrared, 24mm at f/8. Works great for this. Color comparison shot, 24mm f/11. Full frame edges are soft. Close focus 70mm f/5.6 Note bokeh of highlights is poor. Summary Truth be told, modern 24-70mm lenses annihilate this Tammy, particularly in the corners, but that doesn’t mean you can’t take good pictures with it. The bokeh isn’t very good, if that’s important to you. It’s very small and light, which I love. I find this lens most useful to me when I shoot infrared on full-frame. IR is inherently slightly soft anyway, so the lens resolution isn’t much of an issue. You can pick this lens up for less than the sales tax on the other modern lenses of this focal range. #review

Darktable is a free multi-platform, raw-image editor and camera control program. It uses ‘sidecar’ technology, which leaves the raw image files untouched and saves all edits in an “.xmp” file (one per photo). Since Darktable receives ongoing support, it is capable of editing raw files from your new digital camera. I’m reviewing version 2.4.4 for Windows10 x64. You can download Darktable for Windows from here. User manuals from the authors are available. The link to the English version is here. Darktable The Darktable program is geared toward managing the entire workflow of image editing, grading, storage, and retrieval. The workflow is divided into the following five areas: Import/export (lighttable) Image editing/grading (darkroom) Slideshow Print Camera control (tether) The supporters of darktable (at darktable.org) have provided pretty extensive documentation, and many of the dialog samples in this article are taken from that documentation. Many software helper tools mentioned in the documentation only apply to Unix/Linux platforms. I wasn’t entirely happy with the darktable documentation, so I thought I’d take a stab at creating some documentation myself. This program is very powerful, and in many ways I find it superior to Adobe Lightroom. Darktable is a complicated-enough program that I felt it was worthy of a few articles. This first article is going to give a gentle overview of its main features, without going into extreme detail. One of the best features of darktable is its masking capabilities. I’ll only give a light touch on the masking topic now, because I feel it’s worthy of a more extensive treatment in a future article. No, darktable doesn’t support the Nik/Google/DxO plugins; at least not yet. This is probably my biggest disappointment with darktable. Lighttable Lighttable dialog The image import/export dialog is called “lighttable”. It is recommended that you import photos in chunks of single folders, versus recursively importing multiple folders. It’s possible to connect to a camera via USB and import from there directly. If you desire, you can filter the import to omit ‘jpg’ files, etc. There are many configurable options for Darktable, which you access via a little “gear” button near the top-right of the screen. The left-hand panel is generally used for image importing. You can hide/show this panel by clicking the little triangle on the edge of the panel. After your photos are imported, you click on “collect images” and “recently used collections” to select the folder images you want to display and make available for editing. As a side note, you can go back to any folder you have already imported from and re-import. Only the new image files will get imported; you won’t get any duplicated imports. The lighttable right-hand panel is generally for exporting edited images in formats such as jpg and tif. Once multiple images are selected, the “selected image[s]” option lets you delete them or make an HDR image from bracketed shots. Once an image has been edited (inside ‘darkroom’), its history of editing steps can be copied/pasted into other image files. Access this feature from the right-hand panel “history stack”. This is how you can achieve ‘batch’ editing. To paste the history, first multi-select the target thumbnail pictures and then select “paste” or “paste all”. The “paste” lets you select just pieces of the history stack, versus every single editing step. Because lighttable doesn’t use a conventional menu system, you can see how busy its interface can get. For most people, it would probably take a few days of use to get comfortable with this interface. Most buttons have “tooltip text” if you hover over the control, so be aware of this feature. Darkroom Darkroom dialog The image-editing dialog is called “darkroom”. The left side panel in darkroom is mostly informational, including the photo EXIF information and the editing history. The darkroom editor adaptively uses this EXIF information in a few of its edit module settings, such as the ISO setting and camera model, and lens type. The right-hand side panel holds the selected file histogram and a collection of editing modules below the histogram. The histogram can be used to adjust exposure and the black point, depending upon if you mouse-drag in the right or left sides of the histogram. The bottom of ‘darkroom’ has a film roll, as selected by the ‘lighttable’. You can navigate through the photos via the mouse scroll wheel, the spacebar, and the backspace key. Double-click an image to edit it. The top-left of the ‘darkroom’ view shows a small image of the entire photo. Drag the rectangle inside it with the mouse in order to pan through the photo, or just drag inside the large edited image to pan. Just to the right of this little image view is a control to select common zoom levels. There is no “save” option in darkroom, because all edits are automatically saved into a “history stack”. This history stack can be copied/pasted into other image files to perform batch editing. You can click Ctrl-Z to undo the last edit (history) step. If you click on one of the history steps in the left-side panel, and then activate a new editing module, all steps after the selected history step will be deleted. Beware of this operation, since it can’t be un-done. Whenever you want to see a full-screen view of your edited image, just click the Tab key. Click Tab again to restore the panels. You can zoom the main image by using the mouse scroll wheel while the pointer is on the image. To view blown color channels in the selected Raw image, click on the little icon just above the film strip that has Red, Blue, and Green squares in it. Next to that button is a light/dark square to view blown highlights in your image. Keep these controls active while you adjust exposure and highlights to tame the overblown areas. Modules The module types are designed to contain a specific type of edit step, such as noise removal, color control, and sharpening. Each module has its own optional mask, which can be either geometrical (brush, circle, ellipse, path) or parametric (such as an adjustable color or luminance range). The edit modules will be applied in a fixed, carefully controlled sequence of steps. This means that you can choose editing steps (modules) in any order you like, while the output results will have the steps applied in an optimized order. As an example, image sharpening is applied at a later stage than image de-noise. Some of these modules are really smart, and are capable of responding in a customized way to things like the camera model sensor type and ISO setting. To view a module, just click on its name. Beware that making a module visible doesn’t make it active. To make a module active, you need to click its “On” button. The buttons just below the histogram will let you select module categories, such as “Basic”, “Tone”, “Color”, “Corrections”, and “Effect”. When you click on a module name to expand it, the previous module will collapse. The sample module name above is “sharpen”. If you really want multiple modules expanded at once, then hold down the shift key as you click on another module name. If there are modules you use frequently, you can select “favorite” inside the “Module presets” button, shown above. Module Sliders It’s worth mentioning that most modules have “sliders” in them. You can ‘drag’ the slider to change values, and you can also left-click them to make large changes and use the mouse scroll wheel or the arrow keys to make small changes. Masking (module ‘blend’ option) Masks are an integral part of the majority of the edit modules; they let you make changes to selected portions of the image. They can be quite cryptic to understand, until you learn the meaning of the various icons and GUI controls they contain. When you select one of the blend operations “drawn mask”, “parametric”, or “drawn & parametric mask”, you are ready to construct a mask. Since they’re so complicated, I’ll devote a full article to the use of masks in a later article. For now, I just want you to be aware that you can use a different mask with nearly every edit module, by expanding the “blend” option. The “drawn mask” has options to use a brush (drag a circle around to trace a wide path), a circle, an ellipse, a gradient, and a path (to encircle a complicated shape). You can change the size of drawn masks using the mouse scroll wheel. If you use the Shift button with the scroll wheel, you can change the feathering width on the mask edge, and the Control button/scroll wheel will change the opacity of the mask. The “parametric mask” lets you construct an image mask by selecting a characteristic such as range of light or a range of hue. This can enable creating a mask that is far more complicated than you could ever draw with a brush or a path. There’s a little “circle-in-square” button that lets you see where your mask is located, drawn in yellow, when you click it. If you click the “circle-in-square” again, the mask will be hidden. Healing/Hiding Defects: spot removal Spot removal using the circle shape Use the “spot removal” module in the “correction group” to do healing (e.g. clone/stamp). It will let you create circles, ellipses, and drawn paths to fix problems. The usual scroll wheel is available to adjust spot size, while you use the Shift-scroll to adjust the edge feathering width. The shot above shows that the feathering of each circle was minimized, which was adjusted by using the Shift key with the scroll wheel on the mouse. You’d see a dashed line outside the solid line if feathering was increased. The nice thing about this spot tool is how obvious the source/destination indicators are. The source is connected to the destination by an arrow, to indicate how the source points to the destination. Spot removal using a path shape Spot removal paths are created by mouse-clicking along an enclosed path. When you have enclosed the shape you want, just click the right-mouse button to finish it. Your “source” shape is drawn automatically, but it probably isn’t located where you want it. When you draw a “path”, you can hold down the Control button if you want the path edges to be straight instead of curved. You can alter the path shape by selecting one of its “nodes” and drag it after you have drawn the whole path. The source --> destination arrow isn’t shown in the case of a path shape, unfortunately. Drag the source shape over the pixels you want to use to replace at the destination. It will copy the source pixels over the destination pixels and obey the size/feathering/opacity, according to how you use the scroll/Shift-scroll/Ctrl-scroll wheel. If you have fixed up several spots but then change your mind about a previous spot, you can go back and select it with a click and then use the right-mouse button to delete that particular edit without affecting the others. If you leave this module and later return to it, you might find that you’ll need to deactivate/reactivate it to see your previous work (e.g. the source/destination markers). Until you see your previous work shapes drawn, you can’t select them to move/resize/delete them. Perspective Distortion Correction Typical “keystone” perspective problem Perspective correction module This shows an example of a typical editing module. Just click on the button for the vertical correction and also select “automatic cropping”, “largest area”. Two clicks, and the problem is solved. Available edit modules If a module isn’t displayed when you select its group, then activate the “more modules” at the bottom of the screen and scroll down to the module you want and click it. If you frequently use a particular edit module, you can click on its “module presets” button and select “favorites”. “Basic” module group: Crop and Rotate (also has perspective, flip, etc. options) Orientation (only rotates by 90 degree increments) Shadows and Highlights (tame clipped highlights and reveal shadows) Base Curve (alter the manufacturer’s base curve drawn from EXIF data) Exposure Contrast Brightness Saturation Color reconstruction (repair blown highlights) Demosaic (choose algorithm to interpret Bayer filter data) Highlight reconstruction (reconstruct clipped channels) White balance (camera presets, kelvin temperature) Invert (invert scanned negatives) Raw black/white point (activated automatically for raw images) “Tone” module group: Fill light (local exposure modification) Levels Tone curve (operates in Lab color space, however) Zone System (ala Ansel Adams, with selectable number of zones) Local contrast (adjust local contrast, but avoids haloes) Tone Mapping (‘local surroundings’ tone mapping of HDR shots) Global Tonemap (less sophisticated, faster tone map of HDR shots) “Color” module group: Velvia (simulate the film) Channel Mixer (reassign proportions of RGB color channels) Output Color Profile (alter the color profile) Color contrast (between green/magenta or blue/yellow) Color correction (global saturation, tint, split tone) Color checker LUT Monochrome (convert to black and white) Color zones (selectively modify colors) Color Balance Vibrance Input color profile (override darktable auto-color profile allocation) Unbreak input profile “Correction” module group: Sharpen (unsharp mask) You need this on virtually every photo. Make it a “favorites”. Equalizer (local constrast enhance, denoise) Denoise (profiled) Uses camera model and ISO to apply noise removal Denoise (non-local means) Control chroma and luma noise separately Denoise (bilateral filter) High ISO pictures. Uses lots of CPU. Lens Correction Liquify artsy distortions Perspective correction Includes “automatic fit” and “automatic cropping” to fix “keystone” issues with buildings. Spot removal (healing brush) Use circles, ovals, paths. Very useful to hide small skin blemishes and sensor dust specks in the sky. Raw denoise (rid noise before demosaicing) Dithering (help with banding) Hot pixels Chromatic aberrations (lateral chromatic aberration) Haze removal (atmospheric effects adjustment) Defringe (longitudinal chromatic aberration remove) “Effect” module group: Watermark (text overlay) Framing (frame around edge) Split toning (separately alter the hue in shadows and highlights) Vignetting Soften (Orton effect) Grain (simulate film) Highpass Lowpass (Gaussian blur) Can blur with contrast, brightness, saturation. This is the module you’ll want to use for skin retouching in portraits. Lowlight vision (simulate human low light vision) Bloom (highlight blooming effects) Colorize (add a solid layer of color to image) Color mapping (transfer source image colors to target image colors) Graduated density Missing Modules There are a few features that you’ll probably miss in darktable. Here’s a couple examples of how to survive their absence. Red Eye Removal There isn’t any “red eye removal”, but here’s how you could do it: Channel mixer module, and turn it “on”. Select blend: “drawn mask” and place circles over the red pupils (use the mouse scroll wheel to fit the circles inside the pupils). Destination = “red” channel, with red=0, green=0.5, blue=0.5 This procedure will replace the red channel (the red pupils) with an even mix of blue and green instead, which will make the pupils dark. Always make the three channels add up to 1. Infrared Blue Sky Infrared “blue sky” effect from a color white-balanced infrared shot: Use “channel mixer module” to swap the red/blue channels. For destination = “red” channel, make red=0, green=0, blue=1 For destination = “blue” channel, make red=1, green=0, blue=0 Multi-shot Bracketed HDR It’s not really missing, but it’s a bit hidden. In lighttable, do the following: “Collect images”, to get to the folder with exposure-bracketed shots. This is on the left-hand panel. Select the already-aligned shots (use Ctrl and Shift keys). “selected image[s]” from the right-hand panel. Pick the “create HDR” option to make a DNG HDR file. Select “tone mapping” module in darktable to adjust the HDR file to taste. Single-shot HDR To merge an image with 2 more copies of itself, with the other copies over-exposed and under-exposed. Take a single shot, then apply the “base curve” module “fusion” option. Select the fusion “three exposures”. Select an exposure shift (typically 1 stop, or EV). Select an exposure bias of 0 to maintain overall lightness. Select the “tone mapping” module and adjust to your taste. A Typical Darktable Editing Session Start Darktable Go to the “light table” tab Import | folder Browse to your disk folder of raw image files Click the folder, then click “Open”. Images will be imported. Click the “collect images” button and select your imported folder, if you can’t see your desired thumbnails. Double-click on the desired image thumbnail to edit. (it goes to the “darkroom” tab automatically) Click the “blown highlights” button above the filmstrip, just in case. Click on the “Basic” modules icon (a circle icon) Click on a desired edit module, such as “shadows and highlights” Click the “On” icon to enable the module. Make adjustments (decrease highlights, for instance, until the blown highlights in the photo go away). Press TAB to see the edited image full-screen, then TAB to restore. Use the mouse scroll wheel while over the edited image to zoom in/out. (Select/turn “On” other modules and make more edits) Click “Ctrl-E” to export the edited photo into a subfolder of the raw shot, called “darktable_exported”. Tethering Connect and control your camera via USB. You can adjust exposure settings, white balance, focus mode, and even see your camera Live View on the computer. This tethering module lets you do HDR bracketing and time lapse shots. There are alignment guides and overlays that you can add to your screen as well. Behind the scenes, darktable is using the “gphoto2” program and its command-line arguments to control your camera. The people at gphoto.org are actively supporting this multi-platform tool, and it now supports hundreds of camera models from all vendors, including Nikon, Canon, Sony, Panasonic, Olympus, and Fuji. Make sure you charge you camera battery before using this; it’s a pretty heavy energy drain to be using Live View and USB continuously. Summary Don’t be afraid of this program just because it’s free. This is really good stuff, and it’s still actively supported, as of this writing. Since darktable doesn’t alter your raw photos (it just alters the sidecar files) you aren’t faced with any risks to try it out. Maybe someday the darktable.org people will add plugin support, which would make this program truly powerful. As I had mentioned, I'll be adding more articles about darktable features in the future, in an attempt to demystify some of its more advanced features. #howto

If you haven’t read it, you should take a look at my Darktable Overview article prior to reading this . It will give you some needed context for the use of this masking discussion. Masks let you make changes to selected portions of the image. Most of the Darktable “darkroom” edit modules have a blend option, which is where you access the masking operations. The blend operation has options for “drawn mask”, “parametric”, or “drawn & parametric mask”. The default blend is “off”, or no masking. Until you select something other than “off”, you won’t see any masking controls. Any photo editor that doesn’t have a good set of masking tools just isn’t fully useful for me. This is the main weakness of Adobe Lightroom, in my opinion. Darktable has what you need. Drawn Mask The “drawn mask” has options to use a brush (drag a circle around to trace a wide path), a circle, an ellipse, a gradient, and a path (to encircle a complicated shape). You can change the size of drawn masks using the mouse scroll wheel. If you use the Shift button with the scroll wheel, you can change the feathering width on the mask edge, and the Control button/scroll wheel will change the opacity of the mask. A typical module “blend” mask dialog: the “drawn mask” You’ll note in the above “drawn mask” dialog, you get icons indicating (shown left to right) a brush (looks like a pencil), circle, ellipse, path, and gradient. To see the masking bounds, click on the little “hole in a square” icon at the bottom of the dialog. The mask bounds will be rendered in yellow. Pure yellow will indicate an opacity of 100%, for the full masking effect. The icon is a toggle, so click it again to hide the yellow mask. You’ll generally want to enable this feature while you draw the mask, but if you don’t, there’s still an indicator of where you draw. To toggle the module actual masking effect on or off, click on the “eye” icon at the bottom of the dialog. The “blend mode” is used to alter the extent of the mask effect on the selected pixels, such as color, lightness, or normal (all). The mask tool (such as the brush) size is controlled by the mouse scroll wheel. The mask hardness is controlled by Shift-scroll, and the opacity is controlled by Ctrl-scroll. You can also “invert” the “drawn” mask effect by selecting On/Off for the “invert mask” near the bottom of the drawn mask dialog. After you draw a mask (and release the left mouse button), you can alter it after the fact. Click the “view mask” icon (square with a hole in it) to make the yellow mask visible. Click on the drawn mask to select it, and you can still use the scroll wheel to alter its size, feathering (with shift-scroll), and opacity (ctrl-scroll). There are also little square “handles” along the mask path you can select and drag. If you want to rid the path, just click the right mouse button when the mask is selected. If you leave the module and later return to alter the mask, you’ll need to click the “edit mode” button to the right of the “drawn mask” text. The button looks like an arrow pointing at a dashed line. If you want to prevent mask alteration, just re-click the same “edit mode” button. To draw a path for a mask, use the mouse to left-click some nodes on the path where you want it to be (the “destination”). When you have enclosed the shape you want, click with the right mouse button to finish the path. If you don’t want rounded lines in the path, then use Ctrl-click to get sharp corners and straight lines on the path segments. This works great for selecting things like a box. In this case, just enclose the straight-edged shape without having to right-click to finish it. In the path “edit” mode, you can change nodes back and forth between smooth and straight by using Ctrl-click on the node. To alter the path, use the left mouse button to select the path and also to select nodes to drag. Path mask showing the nodes that define it You can delete a path node by first selecting the node (it gets highlighted) and then right-click. Be careful, because if you just select the path and right-click it, the entire path will be deleted. Mouse-scroll to alter the size of the whole path, and use Shift-scroll to alter its edge feathering. Parametric Mask Blend: “parametric mask” A module “parametric mask” blend selection will draw a mask based on pixel characteristics, instead of where the pixels are in the picture. If you want to select something like a garment by its color or a light background, this is what you would use. You can generate some extremely complicated masks with this technique, which would be impossible to manually draw. Depending upon your edit module’s color space (e.g. Lab space or RGB), the dialog will look different. The example above is for Lab color space, where “L” is “lightness”, “C” is “chroma” (saturation), and “h” is “hue” (color tint). If you select “L”, the slider bar will switch to black-and-white. To select a photo color, use the eye-dropper “color picker” icon (shown above). To invert a color channel, click on the “invert” icon as shown above. There is also a “reset” icon to return to default settings. There will be a little white vertical bar (see the “picker color bar” above) drawn on the “input” slider to indicate the color picker selection. Triangles above and below the little “picker color bar” must be dragged to narrow the selection range (from 100% to 0% opacity). The range inside the solid triangles will be 100% opacity, and the hollow triangles control the extent of the mask feathering. If you don’t slide the triangles to narrow the selection, the whole image will be selected by the mask, and your image will be a giant yellow rectangle. Just like the “drawn” mask, the parametric mask has an “eye” icon to turn the mask effect on/off and the circle-in-square icon to view/hide the yellow mask itself. You’ll need to exhibit a little patience when clicking the “eye” to see the effect fully rendered on your computer. Drawn and Parametric Mask Drawn and Parametric Mask, parametric shown It’s possible to have both kinds of masks in a single module, called “drawn & parametric mask”. Shown above, I selected a small area of the structure (via the eyedropper) and made a parametric mask of the “L” channel, where I dragged the little input triangles to select a range of “lightness”. I clicked on the “show mask” button, so the masking results can be seen in yellow while I adjusted the slider triangles. Note the parametric mask sliders are shown in black-and-white here, because I chose the “L” channel. If I had chosen the “h” channel hue, then the slider would be shown as full-color. The mask above “spilled over” a little bit from what I wanted. This is really common with parametric masks. You typically need to do some cleanup using a drawn mask. Drawn and parametric mask, path ‘drawn’ on top of parametric Shown above, I used the “path” and drew over the parametric mask to add some more masking. The little “toggle polarity of drawn mask” is set to a “+”. This lets me erase part of the parametric mask using a drawn mask and clean up its boundary. This demonstrates how I was able to combine the two kinds of masks together. As shown above, I held down the Control key while clicking the points for the drawn “path”. This keeps the mask edges straight, instead of rounded. I used the “Shift-Scroll” mouse scroll wheel to reduce the drawn mask path feathering. Since I wanted this path to be an enclosing shape, I clicked the right mouse button to complete the shape. Portrait retouching mask If you’re a fan of using Gaussian blur on skin when retouching portraits (you probably should be), I’d recommend that you set the mask “opacity” slider (just underneath the “blend mode”) to something around 90% for starters. You want a little skin texture to peek through the mask. You’ll probably be using the “brush” drawn mask the most for this. Lowpass, Gaussian blur with mask to avoid eyes, mouth, nostrils The “effect” group “lowpass” module is what you want to be using for Gaussian blur. Summary As you can see, there are many, many mask features in Darktable. I hope this little guide will help ease the pain of learning how it all works. #howto

Darktable can do more than edit your photos; it can also help you capture them with your camera attached via a USB cable. This kind of photo capture is known as tethered shooting. Darktable uses a program called gphoto2 to control your camera. If you haven’t read it, you should probably read the first part of this series on Darktable here. If you are using Windows, then there is some setup you’ll need to do before you can use Darktable to control your camera. If you don’t do this, then Darktable won’t be able to see your camera. Tethered shooting in Darktable To enable Darktable under Windows 10 to see my camera, I had to download the program called Zadig-2.4.exe (or whatever is most current). I got the zadig program at http://zadig.akeo.ie/ , as shown below. Zadig download site To use this program, start by connecting your camera via USB and turn it on. Next, run zadig-2.4.exe and select Options | List All Devices. You should see your camera in the list; select it. Select your connected camera When you see a screen like what’s shown above, click on “Replace Driver”. It should set up the proper device driver that enables gphoto2 to communicate with your camera. Successful driver replacement for your camera Now, you should be able to use Darktable tethering for remote camera control. Stop the zdiag program, but leave your camera connected and turned on. Don’t turn on Live View on your camera, because it needs to be controlled from Darktable itself. I can’t promise that this driver won’t affect other camera communications software. Start up Darktable, with your camera still connected via USB and powered on. You should be able to see that your camera is visible to Darktable. Darktable sees your connected camera at startup When you first start Darktable, you should see your camera mentioned just underneath “scan for devices”. If you don’t see it, you may need to click the button to scan. If your camera driver is correctly installed, you should now be ready for tethered shooting. Begin tethered shooting Now that Darktable sees the camera, just click on “tethered shoot”. You will automatically get to the correct screen in Darktable, but you won’t yet be able to see what your camera sees. Start Live View to see your camera’s view on the computer Click the little eyeball button as shown above, in the “tethering” tab, under the expanded “live view” option. Now, your camera will be placed into Live View mode, although the camera LCD screen won’t activate. The screen update rate is a bit less than what your camera LCD can do, but it’s pretty good. USB 3 connections, if your camera and computer both support them, will of course be much better than USB 2. The “tethering” options will need to be expanded to both view and operate them. Add an overlay to the view: “grid” In shot above, I added a “grid” overlay. There are several guides to select from. You can also “flip” your live view and select “vertical”, if you wish via the same “live view” dialog. Select the shooting mode, depending on if you intend to do single shots, exposure-bracketed shots, or time-lapse shooting. Before you shoot, you’ll want to be able to see the camera settings. You’ll probably have to scroll down to see those settings. Camera shooting properties To change the camera shooting settings, click the little down-arrows next to the current settings in the expanded “properties” dialog. If you want a setting shown above the Live View window, then click the little eyeball to the right of the control, such as “aperture”. You will probably want to change the “focus mode” setting to continuous-focus, at least until you’re happy with the focus. For a time-lapse, you’d of course want to leave it on “AF S”. When everything is configured like you want it, you click on the “capture image(s)” button to start shooting. If you are doing long time-lapse shooting, turn off the “live view” screen update (the eyeball button) mode. Your screen will only get updated with the latest captured shot, which will help conserve your camera battery. You’ll probably want to switch your “program mode” to “M”, for manual exposure, too. By default, your captured shots in Windows 10 will automatically get transferred into a folder underneath your “Pictures” folder on your computer, and not saved into your camera itself. The shots go into a folder named with the current month and day. For time-lapse shooting, the default tethered photo storage option is ideal, so that you don’t have to worry about running out of space on your camera storage card. Summary Darktable is more powerful than most people would think. By taking advantage of the gphoto2 program, its power is greatly increased. Be aware that tethered shooting is power-hungry, so it would benefit you to charge your battery before using this feature. For extended photo sessions, I know that Nikon sells power adapters EP-5B, EH-5A, and EH-5B that allow you to use external power instead of a battery. #howto

There are many times when you want to adjust only a portion of a photo. In Lightroom, you can accomplish this using what Adobe calls an “Adjustment Brush”. Most people refer to this operation as “masking”. This discussion uses Lightroom 6.14. Mask overlay shown in red To show the mask (adjustment brush) option, select the Tools | Adjustment Brush or else just press the “K” key. When using the mask, the mask brush will look like two concentric circles. The inner circle is solid, showing how far the full masking effect extends. The outer circle is dashed, and shows the extent of the mask edge feathering. The start of the mask (the ‘pin’) is a little white circle with a black center. There are two more sliders for masking control called “Density” (mask opacity) and “Flow”, which is the percent opacity per overlapping brush stroke. Change the diameter of the masking brush by using the mouse scroll wheel. Change the diameter of the feathering effect by using Shift+Scroll wheel. View the mask as you draw it by selecting the Tools | Adjustment Mask Overlay | Show Overlay. While you’re drawing the mask, the middle of the brush mask will have a “+” to show you’re adding to the mask. You can also click the “O” letter to toggle viewing/hiding the (red) mask. To fix masking mistakes, click the “Erase” button (shown above). The middle of the brush mask will have a “-“ to show you’re subtracting from the mask. If you decide to get rid of a mask, click on its ‘pin’ marker and press the Delete key. You may have to scroll down to see the “Erase” button. There’s an option to change the color of the mask overlay, in case you’re masking something that’s already a shade of red, for instance. Mask “Effect” menu To choose an effect with predefined settings, you can select from the Effect menu. The “Exposure” setting is shown above. After you select an effect type, you’re free to adjust the sliders to customize the effect to your own taste. In the example above, the goal is to select just the sky. Note above how difficult it is to try selecting only the sky by just brushing. There is a solution to this problem, and it’s called “Auto Mask”. Mask just the sky with “Auto Mask” to select a color If you’re trying to mask an area that has a particular color, then “Auto Mask” is for you. As shown above, I was able to paint the mask onto the blue sky, and it left the white sails alone. In this example, I decided to selectively adjust the saturation. I clicked the “O” key to see the saturation effect, instead of showing the red mask. Adjust the sky saturation After the mask drawing is finished, remember to click “Done” to complete the mask operation. “Soften Skin” effect Use Keys to Control Masks in a Hurry For a common task such as skin smoothing, invoke a mask by pressing the K key. Next, you can select “Soften Skin” from the “Effect” drop-down menu and immediately start drawing with the mask. Use the mouse scroll wheel to adjust the brush diameter and use Shift-scroll for the feathering. To see the overall mask, press the O key to see the (red) mask, and you can toggle it off by pressing O again. If you make a mistake and draw the mask somewhere you don’t want it, then click on the “Erase” button to fix the mistake. Click the “A” brush (next to the Erase button) to go back to adding to the mask where you want it. The “Auto Mask” option might help minimize drawing mistakes, depending upon the color contrast between the skin color and the hair/background color. When you’re happy with the mask effect, click the “Done” button at the bottom of the mask dialog. Enhance an eye iris with a mask To make eyes sharper and more saturated, you can select the mask effect called “Iris Enhance”. Zoom in (Ctrl +) and use the mouse scroll wheel to get the mask to just cover the iris. The left-hand side of the ‘Develop’ window has a little white triangle that you can click and open up a thumbnail view of your photo. Mouse-drag the little white rectangle in the thumbnail view to navigate around the zoomed view and center the eye being worked on. You will need a separate mask for the other eye. Again, remember to click the “Done” button to complete any individual mask. Navigate around the zoomed picture via the thumbnail The shot above shows the thumbnail navigation window, with a white rectangle representing the zoomed view. Drag the white rectangle to see that part of the zoomed picture. Remember that you can use “Ctrl +” to zoom in and “Ctrl –” to zoom out. Conclusion Masking in Lightroom involves memorizing a few keyboard key shortcuts and use of the mouse scroll wheel. I hope this little guide will make it a bit easier to effectively use the adjustment brush. #howto

People who photograph starscapes know all about lens coma, even if they don’t know it by name. Unless you have some high-end optics, this is probably one of your bigger obstacles against capturing distant lights as pinpoints. Especially in the frame corners. Coma is confusingly defined as “a variation in magnification over the entrance pupil”. It means that off-axis light rays (corners of the frame) are focused to look similar to a comet with a tail or a teardrop. Nearly all lenses have this defect to some degree. Keep in mind that optics almost always exhibit a mixture of defects. You probably won’t see a clear teardrop-shaped defect. This article shows you how easy it is to evaluate coma. It’s cheap and easy to do. My go-to lens for photographing stars has been the Tokina 11-16mm f/2.8 DX. If you stick with 16mm, you can actually get full-frame coverage (e.g. Nikon FX sensors) with this lens. There is a price for doing this, however: pretty bad coma in the corners. If you want to see just how bad coma can get, and if you want to see how different aperture settings affect it, then this test is for you. Coma defect ray trace "Pure" coma photo Tokina 11-16mm f/2.8 DX What materials do you need to test coma? I use a small and cheap laser pointer (literally only 2 bucks) to substitute for my ‘star’. You want a really small and intense light source for this test, and lasers are just the ticket. A cheap laser with some aluminum foil and lens tissue As shown above, you will also need a sheet of lens-cleaning tissue and a piece of aluminum foil. I put the tissue/foil layers over the business end of the laser, and hold it in place with some tape. Note the little buttons above: the front one is the laser button and the rear one is for an LED light. It should go without saying, but I’ll say it anyway. Don’t stare into a bare laser beam. During construction of this testing device, don’t point it at your eyes. Foil and lens tissue taped over laser As shown above, wrap the lens tissue and foil layers over the end of the laser, and tape it in place. I wrapped the tape loosely, so it doesn’t activate the laser beam button. I lightly pressed the foil over the dent where the beam is located, so I know exactly where to place a pinhole. I used a small needle to make a tiny hole in the foil. You want this hole to be really small, so that it will act like a distant star in the sky. Laser, hose clamp, and holding fixture I got a little hose clamp to slip over the laser and its button. To activate the laser, use a screw driver to tighten the hose clamp until it just depresses the button. Loosen the hose clamp to turn the laser off again. Verify the laser beam can be seen shining through the little hole in the foil before you turn it off. Next, place the laser/hose clamp onto a holding fixture as shown above. I like this fixture for being able to position small stuff in nearly any orientation. I also use this fixture to hold small items for macro photography. To perform coma testing, I put the test fixture at one end of a room and mount my camera/lens on a tripod at the other end of the room. Focus the lens at or near infinity, and set your camera on ‘manual’. Align the camera until the laser device is in the corner of the field of view, or wherever you want to evaluate coma. If you want to look at long-focal-length lenses, you’ll probably have to move outdoors and try this at night to get the distances you need. Now, get out that screw driver and tighten the hose clamp to turn on the laser beam. Set your camera exposure and get into self-timer mode. Turn out the room lights and shoot away. Check exposure to make sure the laser spot clearly registers in the photograph. Coma test results I’m showing you the results of the coma testing, where the photograph is shown at 100% zoom (pixel level). The beam is photographed very near the frame corner. This test is using a DX sensor, which is only fair. FX sensor corners look much worse (although Tokina probably thought nobody would ever try it in the first place). Really pixel-peeping at f/2.8 and f/4.0 As expected, the smeary coma looks worst at f/2.8. Just one stop down, and the f/4 shot has already nearly eliminated coma. By f/8, the laser dot is really small and nearly perfect. This lens is considered pretty decent in regards to coma, but it certainly isn’t perfect; on full-frame, it gets pretty bad when shot wide-open. Since a lens aperture’s job is to cut off light rays from the outer portions of a lens, stopping down an aperture is the cure for coma. Conclusion As you can see, the test equipment I used is pretty simple. If you really want to see how a lens handles coma, this is how to do it. Notice how you can dramatically reduce coma by stopping down a lens even a small amount. This is, of course, of little comfort to starscape shooters who are after those wide-open shots to drink up every photon of light. #howto

Nikon made a design change that is perhaps the smartest thing they’ve done since 1959. Their new Z6 and Z7 cameras sport their new lens Z-mount with a 55mm throat diameter and 16mm “flange-focal” distance. This design change wasn’t possible for Nikon until they made a camera that got rid of its flipping mirror. On a full-frame camera, the mirror rotates through an arc with a radius of about 35mm, and their F-mount lenses had to have a long flange-back distance to keep clear of this flipping mirror. The F-mount has a 46.5mm flange-focal distance, while its throat diameter (lens rear diameter) is 44mm. F mount versus Z mount Many lenses designed for other lens mounts could have an adapter to fit the new Z mount, if they have a sufficient image circle for full-frame coverage. The main key here is that their flange distance must be longer than 16mm, which most lenses have. These adapters don’t need any optics in them, so the resolution won’t get messed up. The new design means much faster optics, given a larger mount throat diameter and fewer lens elements needed for the shorter flange distance. Fewer lens elements mean less light loss from absorption and reflection. The larger throat diameter means lens elements with wider diameters and less severe surface curvature is required. The larger rear lens element diameters and aperture mean a physically larger area to capture more photons. It’s much easier to design a wide-angle lens when you can avoid the severe retro-focus required for the long flange distance. Retro-focus means the lens focal length is smaller than the distance to the sensor from the rear of the lens. Now, lenses down to about 16mm don’t need a complicated, expensive, resolution-killing retro-focus design. Imagine some of the cool wide-angle lenses we'll see in the future. You get less chromatic aberration, due to the large throat diameter permitting the less severe surface curvature in the lens elements. More light rays hit the sensor edges at a less steep angle from the larger diameter rear lens element, so conversion of the photons into an image is more efficient. Vignetting can be reduced. Being closer to the sensor and a wider rear diameter, the light rays have a shorter travel distance to the sensor edges. This directly leads to higher resolution throughout, but particularly in the corners. The simpler wide-angle designs will lead to sharper, cheaper, brighter optics with many fewer lens elements. Telephoto lenses benefit less from the wider throat diameter, but you still can make brighter optics via the larger lens elements at the rear of the lens. Of course, the camera body thickness can also be reduced by about (46.5 – 16) mm or 30.5mm. The larger physical rear lens diameter means more room to provide a larger and more powerful focus motor. Except for losing the auto-focus capability of the Nikkor “AF-D” lenses, their FT-Z adapter still lets you use your existing F-mount lenses. Way to go, Nikon. #review

I wanted to alert you about an update for both the Contemporary and Sports versions of the 150-600 mm lens. Sigma announced this update to fix an overexposure problem with using the Sigma TC-1401 teleconverter when using the Nikon D500. Sigma cautions that you will need to update Sigma Optimization Pro to version 1.3 prior to updating to version 1.4.1 if you’re still using the old version 1.1 or earlier. Their download page is located here. You of course need to have their USB dock to perform this lens update. Their Sigma Optimization Pro software will then update your lens firmware to the latest (1.02) when you connect the lens/dock to your computer. This is still my most-used lens I own. If you haven’t tried it (or their new 60-600 version), you should. I’m not getting anything from Sigma to say this, either. #howto