Sigma lets you program their “global vision” series of lenses with their USB dock. This includes the Sport, Art, and Contemporary lenses. One of the things you can program is which autofocus algorithm to use. You get three algorithms to choose from: “Fast AF Priority”, “Standard AF”, or “Smooth AF Priority”. By assigning a different algorithm to different custom switches on the lens (C1 and C2), you can change your mind on the fly and pick the appropriate focus algorithm to fit the shooting conditions. The “Smooth AF Priority” algorithm is primarily for video use, so I never use it (it’s the slowest focus algorithm). I’m interested in getting the fastest focus performance that I can get, so I want to use the “Fast AF Priority” whenever I can. I have already measured the speed of the “Fast AF Priority” algorithm versus the “Standard AF” algorithm, and found that the Fast algorithm is about 20 percent quicker than the Standard algorithm. I had used a Nikon D500 and the Sigma 150-600 Contemporary for the speed test. I thought I’d try to determine just how repeatable the focus algorithms are. If a camera/lens combination is super fast to focus but is totally unreliable at getting to the correct target distance, then you haven’t really gained anything. I decided to use my Sigma 70-200 f/2.8 Sport lens for this test. I have programmed the C1 switch for the “Fast AF Priority” algorithm, and the C2 switch is programmed with “Standard AF” (“Standard” is also Sigma’s default algorithm if you don’t program the lens). I used a Nikon D850 for the tests. All of the test shots were done at 190mm and f/2.8 from a distance of 1.88 meters. This is a fairly close subject distance, but I wanted to do a test where I could spot even tiny focus errors. Sigma Custom Switch (C1) settings options The screen above shows how to access the autofocus speed options, via the “AF Speed Setting” button. It also shows how my C1 lens switch is currently programmed with the “Fast AF Priority” and “Moderate View Mode” optical stabilization on my 70-200mm lens. All of the same options are available for the C2 lens switch. Sigma’s available programmable AF Speed algorithms The picture above shows you the three autofocus speed selections that are available for programming a lens with their Optimization Pro software and their USB dock. You can always change your mind and reprogram the lens later, if you’re not happy with a selection. Sigma already upgraded the firmware in their 150-600 lenses, which vastly improved focus speed. If I hadn’t purchased their USB dock, I couldn’t have taken advantage of their improvements. Focus Comparison Testing Procedures To perform the tests, I would start by first selecting the desired (already-programmed) custom switch setting. I mounted the camera onto a sturdy tripod, because it’s critical to keep the camera at a fixed distance from the target. The camera was set to phase-detect autofocus, with all of the same settings I’d use for regular action photography (where I want fast autofocus). I only used unsharpened raw format for the testing, although jpeg can be used here if you aren’t concerned with accurate target edge resolution values. I mounted a focus target that is designed for focus evaluation/calibration using the free MTFMapper software. The target is designed such that the (middle) camera focus sensor only sees a single high-contrast edge, and won’t be confused by neighboring details to focus on. The target is mounted at a 45-degree angle relative to the camera sensor. This makes it easy to determine what’s in focus and what isn’t. I focus on the middle of the target, where the big vertical trapezoid edge is located. When the target is rotated about the vertical, the trapezoid shape starts to look like a rectangle. I focus with the lens wide open, so that there will be no room for doubt about where the plane of best focus ends up. This is, by the way, the same basic setup that I use to focus fine-tune my lenses at close distances. I have bigger targets for focus calibration at longer distances. To spice up the test a little bit, I shot the photos at a light intensity of EV 7.3, which is typical indoor room lighting, and definitely more of a challenge for a focus system than sunlight. The Focus Target The photo above shows what the focus target looks like. The little blue numbers on each little slanted square are resolution measurements for each measured edge. These numbers are placed there via the MTFMapper program when the photo is analyzed. I’m using a small target, which has overall dimensions of just 8.5 inches tall by 9.5 inches wide, plus some whitespace around that. I want small little squares so that I can discern very small focus errors. The “large” vertical target edge I focus on is just 2 inches tall, and each little square is just a quarter inch on an edge (6.4mm). Since the test shots are done with the target rotated by 45 degrees, the little squares in front and behind the large black target edge go quickly out of focus, and have a very low corresponding measured resolution number. Ideally, the highest resolution measurement would be the large vertical edge in the middle of the shot, since that’s where the focus sensor I’m using is aimed. The little squares that line up with that large vertical edge should have a similar resolution number (assuming the camera sensor edge is aligned parallel to the chart). I start by manually shifting the focus well away from the middle of the target and press my “AF-ON” button to initiate autofocus. If all goes well, then the camera will of course focus perfectly on the large vertical edge in the middle of the field of view. The resolution reading (little blue number on the edge) should be highest on that same edge. I repeat this procedure over and over again; each time I de-focus the lens and press the AF-ON button to re-focus on the target edge and then take the shot. Reality rears its ugly head, however. The resolution measurements will show where the lens actually ended up focusing. If you have quality equipment and have properly calibrated the focus “fine tune”, the best focus should at least be “near” to the desired focus distance. The camera’s phase-detect sensors will tell the camera when focus is “good enough”, and the camera then tells the lens to stop focusing. If you were to shoot in really dim lighting, then you may experience focus-hunting; use bright-enough lighting that your camera doesn't have to struggle with this test. This test, then, is to evaluate the range of distances where focus ended up while using first the “fast” autofocus algorithm (C1 switch), and then using the “standard” autofocus algorithm (C2 switch). Examining the focus target up close In the shot above, I had turned the focus target upside-down, so that the right side of the target is rotated away from me. As you can see, the zone of sharp focus is really narrow. In this shot, the focus was perfect, and the little squares aligned above and below the large vertical edge have the highest resolution numbers (0.18 cycles per pixel). You might notice that your camera will tend to focus too near if you start your focus distance setting in front of the target. As soon as the camera thinks focus is “good enough”, it stops the focus action. If you start from the far side of the target, the focus can tend to be too far (once again, it entered the “good enough” zone and stopped). Keep this in mind when performing focus fine-tune calibration; do a set of shots starting focus nearer and then a set of shots beyond the focus target to verify your camera’s focus behavior. My Nikon D850 doesn't suffer from the stop-focus-too-soon problem, no matter if I focus near-to-far or from far-to-near. Test Results I couldn’t detect any difference in the tendency to miss focus with either the Standard or Fast autofocus algorithms. I did half of the tests starting focus too near the target and half starting focus beyond the target; it didn’t alter the results. I didn’t have a single focus miss of more than 7mm at 1.88 meters target distance, no matter which focus algorithm was chosen. I shot about 100 tests overall, to best determine “average” focus behavior. Never make a focus determination on the basis of a single shot; this is one of those “statistical” things. With either focus algorithm, the focus was on average within 3mm of perfect. I had previously done this same testing procedure on my Sigma 150-600 Contemporary lens. I didn’t see any accuracy or repeatability problems by using the Fast algorithm instead of the Standard algorithm on that lens, either. This doesn’t, of course, guarantee that all of Sigma’s lenses behave this well. Always "trust but verify". Here, then, is a case where you get it all: speed, repeatability, and accuracy. If there aren’t any focus repeatability differences between the Fast and the Standard algorithms, then why would you choose the slower Standard algorithm? I have kept my C2 switch programmed with the Standard algorithm as a sort of insurance policy, but I haven’t needed it yet for general photography. It may be that in extremely dim lighting the Standard focus algorithm might be more reliable, but I haven’t tested it. I’ll leave that task to the reader, as they say. I tried to describe my test procedures in painstaking detail, in case you want to verify your own Sigma lens/camera combination. The autofocus algorithm choices, not to mention all of the other programmable choices, are of course unavailable to you if you don’t get the Sigma USB dock. For me, the ability to customize my Sigma lenses using their dock has made all the difference. #review

If you have to deal in using long exposures or image stacking, here’s a gizmo you might be interested in. The Flashpoint Wave Commander can control taking a long series of photographs. You get to specify how long to wait before taking the shots, the shot duration, how many shots, and the delay between shots. Flashpoint Wave Commander You can see the plug-in cord for the camera. This part is what you can replace to fit other camera models. Use the multi-direction control and its “set” button to program it. The Flashpoint shutter release button is the big round button shown on the left. Connected to camera’s 10-pin plug The Flashpoint connects to your camera’s remote control input plug (e.g. the 10-pin plug on my Nikon D500 and D850). It’s modular, so you can buy cheap (about $8) separate plugs to fit many Nikon, Canon, Sony, Samsung, Matsushita, Pentax, Olympus, and Panasonic cameras. I endured a lot of tedious photography of things like star-scapes and infrared landscapes using my watch to monitor shutter times from around 15 seconds to 4 minutes. I finally got smart and got this unit. This intervalometer lets you specify how long to wait before you take any shots, how long the exposure should be, how many shots to take, and how long to wait between shots. It’s really easy to set up, and it remembers your settings for the next time, unless you turn if off. It has a beeper, if you want sound, and also a screen backlight for night photography. A pair of AAA batteries powers the unit. You can set any of the times from 1 second through 100 hours, and you can take from 1 to 399 shots in a sequence. Just press its little start/stop button to start the program running. To configure your camera to use the intervalometer, you need to be in “manual” mode, and set the shutter on “bulb”. Set the “single-shot” mode, also. Make sure you’re in “release-priority”, so that the camera won’t freeze if it isn’t in focus. It’s also wise to close the eyepiece shutter (or your viewfinder blocker) so that light can’t enter the viewfinder during the exposure. Even though my Nikons have intervalometer features built into them, I find this device superior. And the price is right. It is “wired” to your camera, but once you program it, you can start it and walk away until the program finishes. You can also use this remote as a simple wired shutter release, even if its batteries go dead. If all you want to do is take a photo without camera shake, then just connect the unit (don’t even bother to turn it on) and press the Flashpoint’s shutter release button instead of its start/button. Simple. I don’t get any money from these guys, so I have nothing to gain if you get one or not. I just wanted you to be aware that this device exists; I really like mine. #review

If you have a lens that generates that dreaded hotspot in the middle of your photos when you try infrared photography, you may want to try this trick. LightRoom offers the “radial filter”, which you can use to make that hotspot disappear. Most modern lenses are quite poor at infrared photography, because manufacturers no longer take care to use proper internal anti-reflection coatings that are effective against infrared light. There are of course limits to how bad your lens can be, but for many lenses, you can use the radial filter to darken that hotspot and save the picture. The dreaded hotspot in the middle of the shot The shot above was taken with a Nikkor 18-55mm kit lens (Nikkor 18-55 3.5-5.6 GII DX VR) that most websites will report as “good” for infrared photography. I used an 850nm infrared filter and took the shot at f/11. The picture looks ruined to my eye, due to that pesky hotspot. Let’s take a look at what Lightroom can do to try and rescue the shot next. Configure a radial filter to fix that hotspot As shown above, select the radial filter, and click the middle of the hotspot in the picture. Drag the mouse to get the desired diameter for the filter to surround the spot. Make sure to click on “Invert Mask” so that the filter will affect the interior of that circle. Set the feathering amount, so that the edges of the filter circle will blend into the background. You might want to temporarily set the following, also: Tools | Adjustment mask overlay | Show overlay This command will let you see your mask, and it’s quite helpful while you are adjusting the “Feather” amount. After you’re done, select “Hide overlay”. There's also a "Show Selected Mask Overlay" checkbox below the image to turn the mask on/off. Lightroom also lets you change the mask color, if you find it too difficult to evaluate the effect using the default red color. Fine-tune the radial filter Decrease the exposure value, until the hotspot is darkened to match its surroundings. When you’re happy with the mask settings, click “Done”. Go ahead and perform the usual edits after you’re finished using the radial filter. With the infrared filter I used, I usually prefer to turn the shot into black and white. The hotspot is gone Finished shot As you can see above, the hotspot is basically gone. I converted the shot into black and white, which I almost always do with this particular IR 850nm filter. The plug-in Silver Efex Pro 2 can be very helpful in manipulating the shot as black and white, by the way. You have to be careful that you don’t over-expose the shot to the point where the hotspot gets into the “clipping” region in any of the R, G, or B color channels. At that point, you have to admit defeat; the shot’s not recoverable. I have a few lenses that are so-so when shooting infrared. There’s a mild hotspot in each of them, particularly when I stop the aperture down beyond about f/5.6. This simple trick can save the shots that I’d otherwise send into the trashcan. #howto

I have always read that you must turn off your lens vibration reduction when shooting on a tripod. So what happens if you don’t? Are your shots hopelessly blurred? Do all lenses behave equally badly if you forget to turn VR off? Is Vibration OFF mandatory for tripod use? I tend to reject just accepting what I’ve read or been told at face value. So, naturally, I decided to conduct a test to find out for myself. I already know that keeping VR active while using a gimbal head works fine. I decided to test a Sigma and a Nikon lens, in case the two different companies use entirely different technology in their anti-vibration systems. In both cases, I chose their latest-generation lenses that should represent the state of the art in vibration reduction (or “optical stabilization” as Sigma calls it). Really old lenses with first-generation VR might give different results, but for now I wanted to try modern gear. I chose to test the Sigma 70-200mm Sport at 70mm and f/2.8 and the Nikkor 24-70mm f/2.8 E VR at 70mm and f/2.8. In both cases, I used a shutter speed of 1/160. There is also lore that says “don’t go beyond 1/500 shutter with VR active”, which I have also debunked with my “modern” lenses. The Sigma lens was set up with their OS algorithm called “Moderate View Mode”, although all of their OS algorithms are supposed to achieve identical anti-shake results on the sensor. The Nikkor lens was set up with the “Normal” VR reduction mode. Both of the selected VR modes mentioned above are my standard ones to use, and therefore the ones I’d forget to turn off when mounting my camera on a tripod. Believe it or not, I have forgotten to turn off VR more than once. In all tests, I used a really heavy tripod, since a flimsy tripod would probably need lens VR active anyway. I mounted the lenses onto my Nikon D850, and I shot the tests using Live View (with contrast detect) and with “Silent Shutter”, to guarantee that there would be zero camera vibrations. I used a wired remote shutter release. Comparison Resolution Results: Sigma The plots above show the MTF50 resolution (measured in line pairs per millimeter). These 2-D plots show the entire sensor surface results. This kind of plot could be handy in case any vibrations would tend to mess up resolution in either the vertical or horizontal directions. The “meridional” plot measures resolution in what’s often called the “tangential” direction. The “sagittal” plot is measuring resolution parallel to “spokes” emanating from the lens center. The first plot is a “reference”, since vibration reduction is turned off. Center resolution peaks at about an MTF50 of 62 lp/mm. Again, the camera is on a tripod. In the plots above, vibration reduction was turned on while being mounted on the tripod. The resolution in the “VR ON” mode is actually a tiny bit higher, but essentially the same as the “VR OFF” results, within experimental error. I would conclude from these results that it really doesn’t matter if anti-vibration is active or not. I actually took many shots of my resolution target with both VR=ON and VR=OFF. I really couldn’t discern any overall difference between VR active or not. The average MTF50 for 10 shots with VR ON was 62.3, and the average for 10 shots with VR OFF was 60.2 lp/mm. Given the shot-to-shot variation, these values should be considered to be about the same. Comparison Resolution Results: Nikkor The plots above are my reference standard for my Nikkor 24-70 at f/2.8 without any vibration reduction while mounted to my tripod. Peak resolution is about 52 lp/mm With VR active, the results don’t look any different. Again, the camera is on the tripod. Peak resolution looks about the same as with the VR OFF shot. The average of 10 shots with VR ON was 50.2 lp/mm and the average of 10 shots with VR OFF was 50.5 lp/mm. Again, these average values should be considered about equal. Slow Shutter Speeds Is there any concern about VR with slow shutter speeds? I tried using my Sigma 150-600 at 600mm, ISO 64, f/11, and 1/25 second shutter. This is a crazy slow shutter speed for this lens, even on a tripod. VR ‘off’ testing showed a peak MTF50 of 34 lp/mm and an average MTF50 of 31.3 lp/mm. VR ‘on’ testing showed a peak MTF50 of 37 lp/mm and an average MTF50 of 32.6 lp/mm. If anything, leaving VR active helped a little bit. It certainly didn’t harm anything. Conclusion I don’t think I’ll bother to turn VR OFF when I use a tripod for a short period. I will still probably turn it off for extremely long shutter speeds (like several seconds) if for no other reason than to save some battery power. You might want to do some testing of your own if you have some old lenses with ancient vibration reduction hardware. I don’t want to imply that these three different lens test results are guaranteed valid across all lenses (especially other brands). I keep finding that you can’t just take photography rules at face value. Find out what your gear can actually do, and it will enable you to be a better photographer. #howto

You can see wildly-varying lens resolution measurements for the exact same lens model out there on the internet. Do manufacturers really make lenses with that much variation? I think not. Many (most) internet sites that show lens resolution measurement results don’t divulge how their measurements are done. Some sites actually state that they use jpegs of their resolution target straight out of the camera. Those same sites don’t tell you how much sharpening was used for those jpegs. What you do notice, however, is that they invariably show lens resolution results that are “too good to be true”. The way you’re supposed to capture resolution chart images for analysis is with un-sharpened RAW. Only. And leave them that way. Exposure isn’t too critical here, but generally light meters will make black-and-white charts end up with whites looking too grey, unless you boost the exposure a little. Why does it matter how resolution charts are photographed? Because resolution is based upon the transition from light-to-dark on target edges. Modern resolution measurement software is based upon how many pixels it takes to go from the white chart background to the maximum black on a target edge. The faster that transition occurs, the higher the resolution measurement you’re going to get. Details of the measurement process are discussed in this article. How does sharpening of a photo work? By altering the light-to-dark transition on edges of objects in the photo. Do you see the connection? You can basically dial in the desired test results by adjusting the sharpening. Now your test results are meaningless. Internet sites that provide lens resolution information should also discuss what kind of camera was used (assuming the measurements include the use of a camera sensor). The sensor resolution and whether or not the sensor has an “optical low-pass filter” (OLPF) is important information. An OLPF will lower the measurement numbers that get quoted. If you don’t know this information, then you can’t compare one site’s lens measurements against another site’s measurements. I think an example is in order, to prove the point. And because talk is cheap. I am using the MTFMAPPER program, but programs like Imatest work the same way. They all find (slanted) edges in the photo, and count how many pixels it takes to go from white to black. When they know the size of the camera sensor pixels, how many pixels are in a row or column of your sensor, and how big your sensor is, then they can give you resolution measurements in a variety of different ways. You might get readings such as “cycles per pixel”, “line pairs per picture height”, “lines per picture height”, etc. at a particular contrast level (like 50%). The resolution chart with lots of edges to measure The chart shown above is a typical “slanted edge” resolution chart. You photograph it with the lens, camera, aperture, distance, and zoom setting you want to evaluate. Each edge of the little trapezoids will get measured by software to determine the lens resolution at that location in the field of view. For optimal results, the chart should just barely fill the field of view and be absolutely parallel to the camera sensor. The chart should also be parallel to the edge of the camera frame (for an optimal ‘slant’). Resolution Measurement Comparisons RAW, unsharpened chart: How it is supposed to be done Shown above is the two-dimensional MTF50 chart plot, showing the “line pairs per millimeter” (lp/mm) measurements from the un-sharpened Raw photo of the test chart. This is a really good lens, and the peak measurements around 62 lp/mm indicate how good the lens is. This is the picture format of the resolution target that should be used for analysis. Same chart shot, but now Jpeg sharpened in LightRoom. Amount = 36, Radius = 1.0 The moderately-sharpened jpeg of the same chart photo shows some too-good-to-be-true resolution measurements. Everybody would be standing in line to buy this baby, if these measurements were actually legitimate. I used Lightroom to adjust the original .NEF raw photo with very modest sharpening, and then exported it into jpeg format. You see a huge jump in resolution; upwards of 118 for the MTF50 lp/mm measurement. Fake! Fraud! Bogus! Jpg sharpened in LightRoom Amount = 50, Radius = 1.3 I jacked up the sharpening in this version of the same raw original, exporting it with the “Amount” parameter changed from 36 to 50, and increasing the “Radius” parameter from 1.0 to 1.3. The MTF50 now passes 120! Anybody who’s paying attention would start to get pretty suspicious about these measurements. Faker! Frauder! Boguser! The Chart Up Close Let’s take a look up close to see what’s happening in each shot. Unsharpened Raw shot. Numbers are edge “cycles per pixel” measurement. The close-up above is near the chart center, showing the edge MTF50 measurements in units of “cycles per pixel”. The measurement software overlays the measurements onto each of the edges. This is the raw-format shot without any image processing to adjust it. The measurement of 0.26 above, for instance, is an MTF50 of 60.1 lp/mm on this Nikon D850 sensor. In other units, this measurement is 2873 lines per picture height. If this shot was a landscape, the urge to sharpen it up would be overwhelming, but don’t! The jpeg shot above is the same photograph, at the same chart location, but with minimal sharpening applied. The resolution measurements are hugely different, because the edges have a much shorter transition zone between black and white. The fuzzy grey zone between black and white is mostly removed. This is what makes sharpened photos look so much better than untouched raw versions. The measurement of the same edge has jumped from 0.26 c/p to 0.51 c/p, or from 60.1 to an astonishing MTF50 of 117.8 lp/mm. This same measurement is the equivalent of 5630 lines per picture height. Almost like getting your hands on some sort of advanced alien technology. More aggressive sharpening makes the edge transitions even more abrupt, which translates into astronomically high resolution measurements. But those measurements are of no use to evaluate actual lens performance. The same edge here jumps to an MTF50 of 122.4 lp/mm, or 5851 lines per picture height! Outrageous! Conclusion There’s lots of bogus information out there on the internet. This is just another example of how that can happen, couched in the cloak of “science”. Editing tools like the “unsharp mask” definitely have their place in photography, but not when trying to analyze how sharp a lens is. As the old saying goes, “buyer beware”. #howto

This lens harkens back to the early era of Nikon zoom lenses, when everyone was still using 35mm film. It was manufactured from 1989 through 1999. Your Nikon camera needs to have the in-camera focus motor to use this lens; I performed all of the lens tests using my D850. This is a push-pull kind of zoom, which has long since gone out of favor with photographers. At least you don’t have to worry about which direction to twist a zoom ring. If you want to use manual focus, you have to switch the camera focus switch to “manual”. The lens uses 62mm filters, and the filters (plus the end of the lens) unfortunately rotate while focusing. There’s a focus-limit switch, and I’d recommend that you use it. Try to avoid the “full” focus range setting; focusing through the full range is dog slow. The lens has 13 elements in 11 groups. The lens weighs 850 grams. To me, it feels pretty light. It uses the HN-24 screw-in lens hood, although I got a cheap rubber lens hood for it that works just fine. The lens is about 6.6 inches long un-zoomed. The 9-blade aperture can be stopped down to f/32.0 at 75mm and f/40.0 at 300mm. This lens has the old-style full aperture ring with click-stops, but you lock it at the minimum aperture on modern cameras for auto-exposure. The lens barrel is all metal, and it operates smooth as silk. Nikon really went all-out with mechanical tolerances during this era, and its functionality hasn’t degraded at all over the years. There’s no “wiggle” to be found in this lens. It has, of course, a metal lens mount, but there’s no rubber weather seal or any other sealing. The 75-300 has a non-removable tripod collar that doesn’t have any click stops in it. It’s quite solid, although it’s narrower than today’s tripod collars. The lens isn’t heavy enough to make a tripod collar mandatory, but it does help the balance. The collar tripod foot is quite small; I think it should be a bit larger to make it more stable on tripod heads that have plastic or rubber pads on them. This lens predates vibration reduction, and you really notice its absence at 300mm. It’s easy to get spoiled with modern technology. I have to admit that I was anticipating doing little else besides making fun of how poor the sharpness of this lens is. I didn’t give Nikon enough credit, though. If you’re willing to close the aperture down by only about a half-stop, this lens has very good resolution (at least at the shorter focal lengths). The focus distance data (exif data) saved in the photos is garbage. It’s not a “D” lens, so there’s no distance data. It focuses from about 5 feet (1.5m) to infinity. The “macro” range (marked in red on the lens barrel) goes from 5 feet to about 10 feet (3m). The focus “limit” switch keeps the lens inside either of these ranges, depending upon what distance the focus is at when you set the “limit” switch. At the macro setting, you can get down to a magnification of about 1:3.8, which is quite good for a telephoto. Speaking of focus, don’t bother using this lens unless your camera has focus fine-tune calibration or you use live view. This lens desperately requires focus fine-tune calibration or else the results are terrible. Also note that focus calibration changes wildly from short to long focal lengths. Nikon’s mirrorless cameras don’t have in-camera focus motors, so they are of no use here, either. The mirrorless cameras require manual focus with this lens, and also require the FTZ (Fmount to Z mount) adapter. I didn’t notice any distortion in my photographs at any focal length. I didn’t notice enough vignetting to bother fixing it in my photo editor, either. Shots at the end of the article show the extent of vignetting and distortion. There didn’t seem to be much chromatic aberration, which surprised me. I really only noticed it at longer focal lengths with wide apertures. Subjects like small tree branches against the sky are where you see this purple fringing; see the photos at the end of this article. 75-300 lens at 300mm zoom on Nikon D850 The shot above shows the manual-focus ring near the front of the lens. Note the fairly skinny tripod collar and its tiny foot. There’s no wiggle in this lens or collar, though. The rear of the lens has the full-blown aperture ring. Lens at 200mm Focus scale and limit switch up close Note that there is a white infrared focus-shift dot at both 75mm and 135mm just to the left of the visible-light infinity mark. The limit switch (set at the “limit” position) will keep the lens outside of its macro range as shown above. The macro range (5 feet to 10 feet) is the red stripe on the right. Autofocus Speed and Focus Calibration This lens’ autofocus is pretty slow, or reasonably quick; let me explain this awkward statement. After about 30 seconds of focusing frustration, I slid the focus limit switch from “Full” to the “Limit” position; there was a world of difference in speed. With this switch in “Limit”, it would focus from the regular (about 10 feet) near-distance limit to infinity in 0.415 seconds at 75mm. Using the full focus range, it took 0.933 seconds at 75mm (it feels like an eternity). Using the “Limit” switch position at 300mm, it took 0.433 seconds. Leaving the switch in the “Limit” position, focus was pleasantly responsive. I did the testing in good light; my D850 and D500 cameras got the same focus speed results. Lesser cameras are probably a bit slower than this. The first thing I always do with a lens is to focus-calibrate it. An out-of-focus shot is a useless shot. I found out right away that at 75mm, the focus fine-tune setting (-10 on my D850) was nowhere close to what was needed at 300mm. I determined that 300mm needs a fine-tune setting of +10 on the same camera. Major disappointment. Nikon, unlike Sigma, has no way to cope with a focus calibration problem like this other than to tell you to buy one of their mirrorless cameras – oh wait, their mirrorless cameras don’t support screw-drive lenses! I always write the fine-tune calibration settings data on the inside of the lens cap on a sticker (per-camera); it’s too hard to memorize this stuff. If I don’t remember to reprogram the appropriate calibration setting when I zoom in or out, picture sharpness suffers. Chromatic Aberration Worst case chromatic aberration These shots show how bad it can get with lateral chromatic aberration in the corner of the frame (100% magnification). The left-hand f/10.0 shot shows how much it gets improved by stopping down. As the labels indicate, this is at 300mm and the right-hand shot is wide-open f/5.6. The full shots are shown down below; this was taken from about 220 yards away. Given the extreme distance of this shot, I think the lens resolution in the corner of the frame is really remarkable. Infrared Since Nikon added the IR focus-shift white dots on their focus scale, I thought I’d give the infrared capabilities a little test. I used an 850nm IR filter. I found that the focus shift indicators to not be very accurate. I actually needed to shift the distance scale marker more to the left (closer distance) by an additional 3mm beyond the white dot at 75mm zoom. I was impressed by the very minimal hotspot in the middle of the shot (it was only brighter by about 0.3 stops). The vast majority of modern lenses are terrible at infrared, and zooms are the worst. 850nm IR 75mm f/8.0 Resolution I do resolution testing with un-sharpened raw-format pictures. My resolution target is 4 feet by 5 feet, to enable me to be at realistic shooting distances. All tests were done using my Nikon D850 (45.7 MP). I used the MTFMapper program to evaluate the results. I used contrast-detect focus to side-step using focus calibration. As I mentioned above, the phase-detect calibration is all over the place; it depends upon the focal length. I have noticed that this lens prefers distance shots over close-range, especially from 200mm to 300mm. My resolution target (at about 40 feet with 300mm) leaves you with the impression that the lens is worse than it is; some sample distance shots at the end of this article give you a better idea of its sharpness. The resolution measurements are in units of “MTF50 lp/mm”. To convert these units into “lines per picture height”, just multiply by the result by (23.9 * 2.0). For instance, an MTF50 of 40.0 lp/mm is (40*23.9*2) = 1912 lines/ph. The D850 sensor is 23.9mm tall. MTF50 lp/mm 75mm f/4.5 Even at a wide open aperture, 75mm is decent. MTF Contrast Plot: 75mm f/4.5 Test chart center detail with MTF50 lp/mm values shown on edges Test chart corner detail. MTF50 lp/mm values shown on edges MTF50 lp/mm 75mm f/5.6 There’s a huge increase in resolution by stopping down just a little from wide open. MTF50 lp/mm 75mm f/8.0 This is the sweet spot for 75mm. It’s only a tiny bit better than f/5.6, though. MTF50 lp/mm 75mm f/11.0 MTF50 lp/mm 75mm f/16.0 MTF50 lp/mm 135mm f/5.0 MTF Contrast Plot: 135mm f/5.0 MTF50 lp/mm 135mm f/5.6 MTF50 lp/mm 135mm f/8.0 MTF50 lp/mm 135mm f/11.0 MTF50 lp/mm 135mm f/16.0 MTF50 lp/mm 200mm f/5.3 Yikes! Avoid 200mm f/5.3 at all costs. MTF Contrast Plot: 200mm f/5.3 MTF50 lp/mm 200mm f/5.6 Stopping down just a tiny bit from wide open really helps sharpness. MTF50 lp/mm 200mm f/8.0 This is probably the sweet spot for 200mm. MTF50 lp/mm 200mm f/11.0 MTF50 lp/mm 200mm f/16.0 MTF50 lp/mm 300mm f/5.6 MTF Contrast Plot: 300mm f/5.6 MTF50 lp/mm 300mm f/8.0 MTF50 lp/mm 300mm f/11.0 MTF50 lp/mm 300mm f/16.0 This is definitely the best aperture for 300mm, even though lens diffraction is setting in just a bit. Sample Pictures 300mm f/5.6 Macro, 5 feet Believe it or not, this is considered one of the worst settings for this lens. I think the lens did quite well. The background melts away beautifully. This would be an ideal distance to avoid disturbing a butterfly, compared to regular macro lenses. 75mm f/5.6 I don’t see any vignetting here, and the palm fronds are razor sharp. 75mm f/5.6 I don’t see any linear distortion 300mm f/5.6 I don’t see distortion here, either 300mm f/10.0 Very sharp distant branches at about 220 yards 300mm f/5.6 has chromatic aberration & vignetting, but pretty sharp 300mm f/8.0 Decent sharpness Conclusion Before I started testing this lens, I figured there would be little to do besides mock it and talk about how old lenses really show their age. This has been a humbling experience. The mechanical and optical quality is really quite good. By far, my biggest complaint about this lens is the annoying shift in focus calibration as you zoom it. Mirrorless cameras can’t cure it, since they can’t use the screw-drive lenses. It’s easy to imagine many photographers thought it was a generally un-sharp lens, not realizing how to compensate for it. When this lens was introduced, autofocus calibration fine-tune hadn’t even been invented yet. Chromatic aberration at longer focal lengths can be seen in high-contrast scenes, but stopping down greatly improves it. Although my modern Sigma telephoto zooms smoke this lens, I can honestly say that the AF Nikkor 75-300 f/4.5-5.6 takes really beautiful photographs. If you think about the primitive state of computers and software back when this lens got designed, it’s quite amazing what those Japanese engineers were able to accomplish. They should be rightfully proud. Nikon sold this lens for a whole decade; now I can see why it sold for so long.

It’s assumed that when you double your camera’s megapixels that you get all of that new resolution, right? Not quite. Usually, not even close. Hasselblad X1D-50C: 50 megapixels I did a little test using a Nikon D610 (24 MP) and a Nikon D850 (45.7 MP). I didn't have any Hasselblads handy. The pixel count on the tested cameras is thus: D610 = 4016 X 6068 pixels; the D850 = 5520 X 8280 pixels. The linear change is 5520 / 4016 = 1.37 (37% increase in “linear” resolution). You’d typically expect that whatever lens you use, it would now get about 37% more resolution (as opposed to expecting nearly double the resolution going from 24 to about 46 MP).You’d typically be dead wrong. My testing has shown that the limiting factor in resolution is more the lens than the camera. This might not be a big deal if you’re buying a typical DSLR or a mirrorless camera, but I think it’s a huge deal if you’re shelling out about $17,000 for a medium format camera to get those extra pixels. I understand that there are other factors, such as “color bit depth”, but in actual fact the color bit depth isn’t that much different in going from FX-sized DSLR technology to medium format. Similarly, the dynamic range being captured isn’t very different, either. There are a couple of web sites that evaluate camera sensors, and they bear out what I’m talking about. At DXO, for instance, I saw the following: Hassleblad X1D-50C is 26.2 bits color bit depth versus D850 26.4 bits. Hasselblad X1D-50C dynamic range is 14.8 EV versus D850 14.8 EV. Hasselblad resolution: 50MP versus the Nikon 45.7 MP. Now, what’s the price difference? About $17,000 versus $3,000. Wow. I’d be slightly concerned if I were Hassleblad these days. By the way, the autofocus on the D850 smokes the Hassleblad. I didn’t test the Hasselblad; I’d rather buy a car. But I digress. Getting back to resolution gains, I decided to take a look at a lens with a pretty decent reputation: the Nikkor 85mm f/1.4 AF-S “pro” lens. How much do you gain in resolution by switching to a camera with nearly double the megapixels? Let’s take a look. Nikkor 85mm at f/1.4 on Nikon D610 Peak resolution is about 36 lp/mm with the D610. Nikkor 85mm at f/1.4 on Nikon D850 Ouch. You can barely tell the difference between the D610 results and the D850 results. What in the heck happened? The lens itself is kind of “treading water” at f/1.4, and more camera sensor resolution doesn’t get you anything extra. Next, let’s try stopping down that lens, to see if that helps the situation: Nikkor 85mm at f/2.8 on Nikon D610 Nikon D610 gets about 47 lp/mm at f/2.8. Nikkor 85mm at f/2.8 on Nikon D850 Within experimental error, the D850 resolution is no better than the D610 resolution in the f/2.8 shots. The overall resolution gets better when you stop down, as expected, but the lens resolution is still maxed out on the D610; the D850 can’t improve it. Sigma 70-200 at 70mm f/2.8 on Nikon D610 Nikon D610 MTF50 results using the Sigma 70-200 at 70mm and f/2.8 is a better example for resolution comparison. The resolution range is from about 20 lp/mm to 51 lp/mm. Sigma 70-200 at 70mm f/2.8 on Nikon D850 Shifting over to the Nikon D850 shows a resolution range on the Sigma 70-200 at the same 70mm and f/2.8 from about 20 through 62 lp/mm. That’s roughly a 22% resolution gain (or 62/51 = 1.22) by using the higher resolution sensor. We’re still not up to a 37% resolution gain, but I think we’re once again up against a lens resolution limit. Stopping the lens down further, let’s see what we get. Sigma 70-200 at 70mm f/4.0 on Nikon D610 Sigma 70-200 at 70mm f/4.0 on Nikon D850 The D610 center resolution is about 60 lp/mm. The D850 center resolution is around 71 lp/mm. That’s 71/60 or roughly a 16% increase over the D610. You can tell by looking at the two-dimensional resolution results that providing “the lens resolution number” is pretty much a fool’s errand. Resolution is all over the map in different parts of the sensor, and sagittal versus meridional directions are hugely different as well. That’s why I use words like “roughly” and “about”. That’s also why I always show these somewhat messy two-dimensional plots. Conclusion This testing shows why lens manufacturers have their work cut out for them. New camera sensors are now hungry for better lenses. It also shows that you’re wasting your time and money if you think that a new camera is going to make that old lens really excel. The only conclusion that should be drawn from this testing is that the combination of a good lens on a high-resolution sensor will net better resolution than a good lens on a lower-resolution sensor. How much better depends upon many factors; generally speaking, the improvement will be a bit underwhelming. The actual mathematics behind this phenomenon goes like this: System_MTF = Camera_MTF x Lens_MTF The “MTF”, or modulation transfer function, is a measure of resolution-versus-contrast that ranges from 0 to 1.0, where 1.0 would be perfect. This math shows that even a great sensor combined with a poor lens won’t give great results, because the lens drags down the “system”. The same is true for a great lens on a poor sensor. The weakest link in a chain spoils the whole chain. I’m not even considering things like diffraction (by stopping down the lens aperture too far) or poor photographic technique. There’s a whole laundry list of ways to ruin your picture resolution. It’s a good thing that newer cameras offer more features like faster focus, bigger shot buffers, more frames per second, reduced sensor noise, and the ability to basically see in the dark. Increased sensor resolution isn’t going to win them many more fans, unless photographers enter the very expensive avenue of buying new, higher-resolution lenses.

It’s inside every fiber of my being to never, ever take a shot with my camera unless it’s either firmly hand-held or secured atop a tripod. What kind of pictures can you get when you finally get brave enough to let go and lay your camera down? I decided to try some bug-perspective pictures right inside some plants. I haven’t gone totally crazy, though; I brought along a little towel to keep dirt and moisture off the rear of my camera as I laid it down on the ground or inside the nook of some branches. The bunched-up towel was also handy to help aim the camera. Aloe with 8mm fisheye lens I used my 8mm Rokinon fisheye at a short focus distance and stopped down the aperture to f/16. I also used a self-timer or remote control so that I could get out of the way during the shot. This definitely isn’t a general-purpose lens, but it can make great photos with extreme perspective. The effect I’m after here only works with super-wide lenses. You could get improved focus depth using focus-stacking software with multiple shots, but this single-shot technique works pretty well (and avoids problems with wind). For some shots, the 180-degree view and curved lines were a bit much, so I used the Lightroom “lens profile corrections”. This lets you get the lines straight (it becomes a rectilinear lens), at the cost of about 2 millimeters of focal length. I also went straight from Lightroom to my HDR Efex Pro 2. People either love or hate this stuff; I’m in for former group. I waited for cloudy conditions; I think the sky looks far more dramatic with heavy cloud cover, especially with HDR. Camera lying on a protective towel The shot above shows how I would fluff up a hand towel under the camera to help line up the shot. A beanbag would work even better for this, if it’s not too thick (bugs are short). Aloe Ferox from a bug’s perspective Camera resting inside a Protea bush Inside a succulent plant in full bloom If you constrain yourself to tripods or hand-holding, you’re going to miss out on some very interesting picture opportunities. Other than a super-wide lens, you don’t need any special equipment to try this. You obviously aren't constrained to just laying the camera on its back. The key is to get low, close, or underneath. Find a way to get your camera to somewhere you can't get your eye. Make sure you don’t get too cocky and rest your expensive camera on a flimsy branch that can snap off with the first light breeze. You might even consider using a safety line or camera strap to connect your gear to a sturdy branch so it doesn’t accidentally come hurtling out of that tree. Happy shooting.

Ever wonder how your camera and lens focus speed changes with light levels? Everybody knows that focus gets slower in dim light, but by how much? Focus speed is primarily a function of three things. First, the camera tells the lens what distance to focus. Second, the lens hardware (and firmware) has its built-in capability to respond to focus requests. Third, light levels dictate the quality of focus feedback the camera gets to work with. Bad light equals bad focus feedback. There are, of course other variables that can influence focus speed, such as the ambient temperature and the subject contrast. My own tests are done in good conditions (around 70F to 80F) with a fully-charged battery and a pretty high-contrast target. A fast-focus lens Any focus speed measurement is only valid for a particular camera and lens combination. For the tests that follow, I used my Nikon D500. This camera seems to behave almost exactly like my D850 in regards to focus capability. I tested three lenses: my Sigma 70-200 f/2.8 Sports (at 200mm), my Nikkor 85mm f/1.4 AF-S, and my Nikkor 24-70 f/2.8 E VR (at 70mm). For the Sigma Sport, I tried both the “standard” and “high speed” focus algorithms. Surprisingly, they seemed to perform the same at any given light level. My Sigma 150-600 is about 20% faster using its “high speed” algorithm. I measure focus speed via how long it takes to change focus from minimum distance to infinity. For the Sigma 70-200, that means the range is a bit less than 4 feet to infinity. I use the back-button (AF-ON) focus technique while in continuous auto-focus mode and phase-detect focus. As I explained in a previous article, I use my D850 video at 120 fps to film the focus distance scale on the lens. Using this technique, I get a resolution of 0.0083 seconds per frame (120fps) to time the focus action. The f-stop used in testing doesn’t matter, because the camera always focuses with the aperture wide open. I measure light levels by looking at the EXIF data from the photograph, which I get using the “Exiftool” program. This program is free, and invaluable for retrieving a wealth of information about each photo. I had intended to graph my measurement data, until I looked at the numbers. There was almost no change in how long it took to focus, up to the point of failure. In dim light, focus just got unreliable instead of slow. In really poor light, the camera would eventually go through the whole focus range a couple of times and then give up. Graphing this kind of timing behavior would be an exercise in futility. Light Levels I did all of my testing outdoors. After sunshine testing, I waited until sunset. I would take a new shot about every 5 minutes until near-darkness. I did the testing outdoors so that I could focus on a target that was about 200 yards away. For my “bright” light testing, I’m using sun-lit shots in the later afternoon. This isn’t the brightest light you can get, but light levels beyond this don’t provide any improved focus speed. The EV (exposure value) corresponding to this light is around 14.3. I tried light levels all the way down to EV 1.3, which is near-darkness. The only lens to (occasionally) succeed at this level was the Nikkor 24-70 f/2.8, and it started getting unreliable at EV 3.6. Tests that didn’t succeed are marked with a “---“. Focus Time (Seconds) Versus EV Results EV 70-200mm 85mm 24-70mm Notes 14.3 0.358 0.458 0.25 Bright Light 13.4 0.358 0.458 0.25 9.9 0.358 0.458 0.25 9.3 0.358 0.458 0.25 8.9 0.358 0.517 0.25 8.5 0.358 0.558 0.25 8.3 0.358 0.567 0.258 7.9 0.358 0.567 0.258 7.3 0.358 0.567 0.258 6.6 0.358 0.567 0.258 6.3 0.358 --- 0.267 85mm too slow now 5.6 0.367 --- 0.267 4.6 0.367 --- 0.267 3.6 0.383 --- 0.283 50% fail Sigma & 24-70 2.6 --- --- 0.909 70% fail 24-70 1.3 --- --- 0.909 80% fail 24-70 Conclusions I was very surprised by these test results. I remember reading many years ago about cameras/lenses that would demonstrate a smooth exponential decrease in focus speed at decreasing light levels. Lower light levels always meant slower focus. I imagine that old camera technology (and very slow on-board computers) forced this type of behavior. Fast-reacting modern cameras can largely bypass this problem, and they remain very responsive in most levels of illumination. The testing I did (both the D500 and D850) had very little change in focus speed up to the point that they would suddenly become unreliable at focusing. In very low light, the focusing would typically go through the whole focus range twice (near-far-near-far) and then quit. Sometimes final focus was okay, but mostly it would fail. The Nikkor 85mm f/1.4 would get “near” to the correct focus distance, and then really slow down just before achieving final focus (in low light levels). I consider this a “fail”, since it would take about 2 seconds to finish focusing. This lens has always been notorious for being slow to focus (most f/1.4 lenses are). I also noticed that my D850 video (used to capture the lens focus scale action) showed how pathetic its contrast-detect focus was in dim light. It would end up hunting back-and-forth, rarely locking on the target. I totally understand why cinematographers stick with manual focus. Each lens/camera combination you own probably has its own focus behavior fingerprint. Knowing how your gear behaves before you go shoot something important might just save the day. There’s a reason why lenses have that manual focus ring on them.

This isn’t something that I’d recommend doing, but I know that there are many people interested in putting Sigma’s TC-1401 1.4X teleconverter onto the Sigma 150-600. Sigma has even sold this combination as a kit. So here goes. Sigma TC-1401 1.4X teleconverter on Nikon D850 The field of view at 840mm is outrageously narrow. On a DX camera, at a 1260mm equivalent, it’s even outrageous-er. I know that isn’t a word, at least not until you try this combination. The Sigma 150-600 Contemporary is a good lens, but at 600mm it’s pretty much at the limit of its abilities for quality resolution. Adding a teleconverter into the mix certainly isn’t going to help. The camera focus system isn’t going to be thanking you, either. A 2X teleconverter would be out of the question on this lens, both for resolution quality and the ability to auto-focus. I would be remiss if I didn’t remind the audience that you have to attach your Sigma teleconverter to the lens prior to mounting it to the camera. If you don’t follow this procedure, then it won’t autofocus. Resolution tests I performed a resolution test with the lens/teleconverter combination at 840mm and f/9.0, which is with the aperture wide open. This means that the lens was zoomed to its maximum 600mm marking, getting a combined focal length of 840mm. The aperture of f/9.0 is about as dim as I’m willing to photograph moving subjects. Quality will of course improve some when you stop down the aperture. I figured that there isn’t much sense in testing this teleconverter at small focal lengths, since it would be much wiser to merely remove the teleconverter. If somebody bothers to put a teleconverter onto a lens that already zooms to 600mm, it means they want as much reach as they can get. I photographed a resolution test chart from 62 feet (!) or 18.84 meters. Even from this far away, only a piece of the test chart could fit into the field of view. This is as far away as I am able to get from the target where I do my testing. Even at this distance, I begin to wonder if air turbulence starts to become a factor. I perform resolution tests using “live view” with contrast-detect focus, to eliminate focus calibration from being an issue. I set my camera up to use electronic front-curtain exposure to rid vibrations. I also use a wired remote release. Even contrast-detect focus gives variable results, so I pick my sharpest result (from 10 shots) to report. 840 mm resolution chart detail, Sigma TC-1401 f/9.0 on Nikon D850 The 840 mm peak resolution was measured to be an MTF50 of 32.4 lp/mm. This is an equivalent of 1549 lines per picture height. A common minimum “quality” resolution benchmark is an MTF50 of 30 lp/mm. This result just made it into the “good” category. Note that the exif photo data reported above shows 850mm. You may notice that the other resolution measurements in the shot are less than the 32.4 lp/mm reading. Lens resolution is a lot more complicated than a single number. Generally, these resolution results aren’t too good and fall a bit below what I consider acceptable. The shot above is un-sharpened raw format, and any chromatic aberration would show clearly. You can see a trace amount of it here, although post-processing would easily remove it. There is just about zero vignetting with this combination, as you'd expect. 600 mm f/6.3 resolution chart center, Nikon D850, no teleconverter 600 mm f/6.3 resolution chart edge, Nikon D850, no teleconverter Next, I removed the teleconverter to repeat the test for comparison purposes. Everything else remained the same as the shots that I had taken with the teleconverter attached. The MTF50 peak was measured at 48.0 lp/mm. The equivalent peak resolution here is 2294 lines per picture height. The shot quality looks significantly improved, as expected. The resolution change is 1549/2294, or 0.68, which means a drop of 32 percent by adding the teleconverter to the lens. This is a better result than just cropping the shot, but not by a very significant margin. Focus Speed The cameras I tried (Nikon D850 and D500) struggle to focus with this setup when not in good lighting, but incredibly they can still focus in moderate shade. No birds in flight with this kind of rig, though, unless they’re the big heavy birds. For lesser cameras, focus performance is going to go downhill in a hurry. I measured focus speed with and without the teleconverter to compare the differences. My usual testing involves setting the lens on its minimum focus distance to find how long it takes to focus on infinity. I do these tests in sunlight, so that I can compare various lenses and cameras in good lighting conditions. My tests were at 600mm (or 840mm with the attached teleconverter). I used my D850 on some tests, and the D500 on others. I didn’t notice any focus speed differences between these two cameras. They’re advertised to focus down to f/8 (not all focus points, though). The aperture f/9 didn’t generally pose in a problem in the conditions I use this lens, despite being “out of specification” for the camera focus system capability. If your camera doesn’t have any f/8 focus points, then don’t even consider using this teleconverter. Also, you can notice focus inconsistencies if you pick any non-f/8 focus sensors (try to stick with the center focus point). Without a teleconverter attached, it takes 0.633 seconds to focus through the full range. With a teleconverter, it takes 1.183 seconds to focus through the same range. This is the worst performance I have witnessed from a lens to date. Next, I tried a more “real-world” big lens focus test, going from 50 feet to infinity. I experience conditions like this all the time out in the field. Keep in mind that 50 feet is actually pretty "close" at this extreme magnification. Without the teleconverter attached, it takes 0.125 seconds to focus through this range. With the teleconverter, it takes 0.2917 seconds to focus through this same range. This result is perfectly acceptable in most shooting conditions. Generally, it takes about twice as long to focus when using the teleconverter. For realistic focus distance changes, this is totally acceptable and better than I would have thought. You’re crazy if you routinely focus from minimum distance to infinity out in the field. Conclusion I don’t personally think that adding the teleconverter is worth it for this lens. I’d just as soon crop a shot and get only marginally worse results than using the teleconverter. Stop down the aperture, if your subject isn't moving, for a moderate increase in resolution. I am a real fan of using the Sigma TC-1401 on my 70-200 f/2.8 Sigma Sport, but I just can’t recommend using it on the Sigma 150-600 Contemporary lens.

This article will show you how to make, preserve, and verify an accurate white balance preset. If you have a particular lighting setup that you use frequently, then you should save its white balance calibration to be able to return to it later. Even if you use Raw format and have a photo-editing program that lets you adjust the white balance after the fact, you’ll thank yourself for getting things right before you take the shot. Also, the “Auto” white balance feature of your camera isn’t quite as smart as you might think with non-standard lighting or subjects. If you’re doing a product shot for a client, they probably won’t remain your client for long if the color in the shots isn’t perfect. As an example, there used to be a term “Kodak Yellow”. If Kodak’s packaging wasn’t reproduced perfectly in photographs (or a magazine page), it would be quickly rejected. (Remember them?) To create a perfect white balance, you’ll need a grey card. Your goal is to get shot histograms that have the R,G,B peaks that exactly match each other. To achieve this color perfection, you need to calibrate against a subject that is entirely neutral, like a grey card. I’m going to show you an example using my LED ring light. Under “average” conditions, the color balance is fairly close when using “auto” white balance, but when I am doing macro shots of things like the inside of a flower, the color balance can get awful. This earlier article discusses how “auto” white balance can go terribly wrong. My example procedures will demonstrate two cameras: the Nikon D610 and the D850. You might think that the procedures would be identical, but remember we’re talking about Nikon here. They’re generally loath to do the same thing twice. I give my white balance presets meaningful names, such as “LEDring” because I’d never be able to remember them otherwise. Please note that there are some light sources that you cannot successfully calibrate against. An example of this would be sodium vapor street lights, which don’t contain enough of the full light spectrum. D610 White Balance Preset Procedure Histogram of a proper white balance The shot above shows the D610 capture of a grey card using a white balance preset. The preset used here was the “d-2”. The D610 accepts up to 4 presets. The histogram peaks show that the capture was completely neutral, since the R,G,B peaks align perfectly. I used an LED light source, and the “d-2” preset was calibrated to this light. The procedures that follow show you how to achieve this precise calibration. Note that a non-neutral subject photo can’t be used to verify proper white balance, since the R,G,B histogram feedback won’t show the vertical alignment of color peaks. Capture Your Preset Set up your light to illuminate a grey card Press the WB button (has the ‘?’ on the button) Spin the “main” (rear) dial to get “PRE” on the control panel Spin the “sub-command” (front) dial to choose d-1 through d-4 Release and re-press (hold down) the WB button to get “PRE” to blink Fill the frame with the grey card (it doesn’t have to be in focus) Press the shutter (within 6 seconds, before PRE stops blinking) You should see “Good” on the control panel, if it’s successful You will see “no Gd” if the measurement fails Name Your Preset Go to the “Shooting” menu (the camera icon) Select the White Balance option Press the selector right-arrow Select PRE Preset manual Press the selector right-arrow Choose the preset you used in the capture step, e.g. “d-2” Press the ISO (the “-“ magnifier) button to select the preset You’ll note the preset already shows “d-2:LEDring”, because the preset already had a name. This procedure will let you alter any pre-existing preset name. If you inspect both the “d-1” and “d-2” presets above, you’ll see that they have a little “key” icon at their top-right corner. This key indicates that the preset is protected and can’t be accidentally deleted. The steps that follow assume that the “d-2” preset isn’t protected. Also note that the d-3 and d-4 presets above haven't been assigned anything yet. If they were assigned, a little picture would show behind them. Select “Edit comment” and press the selector right-arrow Edit the comment text using the arrows and the Ok button If you type an incorrect letter, press the “trash can” button Press the Qual (the “+” magnifier) button to save the name Protect Your Preset Select the White Balance | PRE Preset Manual option Press the selector right-arrow Select “Protect” and press the selector right-arrow Note that the screen above shows “Protect OFF”; if it instead it showed “Protect ON”, then you’d know it was already protected. Select “On” Press the “Ok” button to finish The preset selection screen will now have the little “key” icon on the protected preset and you can’t delete it. If you change your mind, then repeat this procedure but select the Protect “Off” choice. Use Your D610 Preset Press the WB button (has the ‘?’ on the button) Spin the “main” (rear) dial to get “PRE” on the control panel Spin the “sub-command” (front) dial to choose d-1 through d-4 D850 White Balance Preset Procedure Histogram of a proper white balance The shot above shows the D850 capture of a grey card using a white balance preset. The preset used here was the “d-2”. The D850 accepts up to 8 presets. The histogram peaks show that the capture was completely neutral, since the R,G,B peaks demonstrate perfect vertical alignment. I used the same LED light source as before, and the “d-2” preset was calibrated to this light. The procedures that follow show you how to achieve this calibration. Capture Your Preset Set up your light to illuminate a grey card Press the WB button on the top left dial (on top of the camera) Spin the “main” (rear) dial to select PRE Spin the “sub-command” (front) to select the “d-1” through “d-8” Release and re-press (hold down) the WB button to get “PRE” to blink Fill the frame with the grey card (it doesn’t have to be in focus) Press the shutter (within 6 seconds, before PRE stops blinking) You should see “Good” on the control panel, if it’s successful You will see “no Gd” if the measurement fails Name Your Preset Go to the “Photo Shooting” menu (the camera icon) Select the “White Balance” menu Press the right-arrow on the selector Select “PRE Preset manual” and press the 'right' multiselector arrow. Select the “d-2” (used in the capture of the LED light) Press the “Ok” button (Note that I had already given this preset a name, which shows when I selected the “d-2” preset). If you inspect the “d-1” preset above, you’ll see that it has a little “key” icon at its top-right corner. This key indicates that the preset is protected and can’t be accidentally deleted. The “d-2” preset doesn’t have this key showing, so it’s not protected. Also note that the d-3 through d-8 presets above haven't been assigned anything yet. If they were assigned, a little picture would show behind them. Select the “Edit comment” Press the right-arrow on the selector You’ll note that the screen already displays “d-2: LEDring” since I had already given this preset a name. This procedure lets you change the name of the preset, if you wish. Use the touch screen to type in the name of the preset Use the trash can button to fix mistakes You use the same procedure to modify the preset name Press the “Ok” button to save the name Protect Your Preset Select the White Balance | PRE Preset Manual option Press the selector right-arrow Select the “d-2” (used in the capture of the LED light) Press the “Ok” button Select the “Protect” option Press the selector right-arrow Note in the shot above that the “d-2” preset isn’t yet protected (it says “OFF”. If it instead indicates “ON”, then you know it’s already protected. Select “On” Press the “Ok” button to finish Use Your D850 Preset Press the WB button on the top left dial (on top of the camera) Spin the “main” (rear) dial to select PRE Spin the “sub-command” (front) to select the “d-1” through “d-8” Conclusion For the occasions where you have a lighting setup that you use regularly, such as a studio, you really should use a calibrated white balance. You don’t want to rely on “auto” white balance, in case your camera sees an unusual scene and makes a poor color decision. Professional wedding photographers will often scout a venue before the event and save the measured white balance(s) from different rooms. Smart photographers will also tack on a name to these white balances, to minimize mistakes during the shoot. If you consistently use flash instead of ambient lighting, then your preset for the room will probably get overpowered by the flash. If you intend to use a preset white balance long-term, then it makes good sense to both name and protect that preset against accidental erasure. Not only will the photo colors be consistently more accurate, but you’ll save a ton of time when you edit your shots.

If you want to explore the world beyond life-size, the Nikon PB-4 bellows is a terrific vehicle to get there. This 70s-era bellows is the best one that Nikon ever made, and you can still find it for sale (used) on sites like eBay. Back in the day, you’d probably have purchased the Micro-Nikkor 55mm f/3.5 lens to use with this bellows. Nikon also sold a 105mm f/4 P lens that you could actually focus to infinity on the bellows! This 105mm lens would allow up to 1.3X magnification forward-mounted on the PB-4. The 105mm gives a better working distance than shorter lenses. This lens is essentially useless without the PB-4 bellows, since it can’t focus by itself. It’s worth noting that the PB-4 bellows has both swing and shift controls. These controls were mainly intended for use with the Nikkor 105mm f/4 P lens. This lens has a large image circle, and in combination with the PB-4 enables you to have the same kind of controls as a “view camera” for manipulating the plane of focus and perspective control. As you’ll see, though, these controls can be useful for any lens attached to the PB-4. As you will note below, there’s a lot of hardware and software involved in quality close-up photography. I hope that this guide gives you a better idea of what gear you will probably want to use. Bellows PB-4 with Micro-Nikkor 60mm f/2.8 AF-D Today, a really good choice for a lens on the PB-4 is the Micro-Nikkor 60mm f/2.8 AF-D, which you can still buy. It’s one of the only lenses you can still obtain new (as of this writing) that has an aperture ring. When you mount a lens on the PB-4, you won’t have any electrical contacts to control an aperture, so you need a lens with a mechanical aperture ring. The Micro-Nikkor 60mm lens works for FX format, which is helpful for its larger image circle. By itself, this 60mm lens will autofocus down to 1X (lifesize) magnification; the PB-4 is for going beyond this magnification. Here’s a rare occasion where you will want to unlock the lens aperture ring, so that you no longer keep it locked at f/32. You will need to alternate apertures between wide-open (to focus) and the shooting aperture. Manually rotate the aperture ring, instead of letting the camera operate the aperture. Please remember to lock the lens back at f/32 before using it for regular photography on your camera without the bellows, or you’ll get the “f EE” error. BR2, BR3, and Step-down rings on 60mm lens For optimal sharpness beyond life-size magnification, most lenses work better when you mount them in reverse. Nikon used to sell a ring called the “BR2”. With this ring, you’d screw it into the lens filter threads and then mount the lens backwards. Unfortunately, the older Micro-Nikkor lenses had 52mm threads; the 60mm Micro-Nikkor has 62mm threads. To mount the BR2 ring onto the 60mm Micro-Nikkor, you need “step-down” rings that go from 62mm to 52mm. You can still buy a new Nikon “BR2A” ring today that does the same thing. Step-down ring sets (and step-up ring sets) are cheap and well worth the investment. To protect the rear of your lens, now that it’s mounted in reverse, Nikon still sells a ring called the “BR-3”. This ring mounts on the back of the lens, and it has a 52mm thread that you can mount a protective filter onto. The BR-3 ring by itself acts like a lens shade. If you have a larger filter you’d like to use, then you can use “step up” rings for these. To mount a modern Nikon camera on the PB-4, the bellows camera mount must be rotated into the vertical (portrait) orientation. After mounting the camera, you can then rotate the camera back into horizontal (landscape) orientation. Note that some camera models have a built-in flash that can slightly rub on the bellows while mounting the camera. The Nikon D610 is an example of such a camera; it still can be mounted, however. Also note that any camera battery grip must be removed before the camera will successfully fit onto the bellows. Models such as the D5 won’t work on this bellows. My Nikon D850 camera fits onto the PB-4 just fine, as long as I remove its battery grip attachment first. It would be possible to use an extension tube on the rear of the bellows to gain enough clearance for cameras to fit onto the bellows. I still don’t think that cameras with grips could clear the rack-and-pinion rails, though. Once the camera is mounted, you can adjust the front (lens mount) and rear (camera mount) independently on the PB-4 rack-and-pinion focus rails. This is how you control the magnification you wish to use. There’s a handy millimeter-marked scale on the side of the focus rail. Swing and Shift Bellows Capabilities Nikon currently sells “PC” lenses, which stands for perspective control. These lenses, however, are only for conventional focus distances and low magnification. The PB-4 bellows, created in 1970, has perspective control built in. This bellows essentially takes over where the PC lenses leave off, to enable perspective and focus-plane control at high magnification and close distances. Swing (rotate) adjustment To change the plane of focus, you can alter the lens swing adjustment up to 25 degrees in either direction about the vertical axis. There’s a friction lever just under the mounted lens at the front of the PB-4 to enable this adjustment. Shift adjustment To shift the center of the subject, you can shift the lens on the bellows up to 10mm either left or right. There’s a separate friction lever at the front of the PB-4 to enable the shift adjustment; it’s near the ‘swing’ adjustment lever. It’s also possible (and usually necessary) to combine both swing and shift at the same time. See the Scheimpflug principle down below; it shows you how to successfully use these controls. You typically use these controls when the (flat) face of a subject doesn’t align with the flat face of the camera sensor. You need to swing the lens until its optical center plane (parallel to the lens diaphragm) intersects both the sensor plane and subject plane. Next, you typically need to shift the lens to center your subject in the viewfinder. Don't worry, I'll explain this procedure a little better in a minute. The bellows only lets you make a swing adjustment about a vertical axis. The shift adjustment is only available along a single axis, as well. Setup to photograph a rotated coin, viewed from above The photo above shows the 60mm lens, the PB-4 bellows, and an LED ring light being used to photograph a coin held in front of the lens. The coin is rotated, so that its face is no longer parallel to the camera sensor. The swing and shift controls were used to get the entire face of the coin in focus. Both the BR2 and BR3 rings were used to reverse-mount the lens and provide an attachment surface for the ring light. This arrangement as shown above results in a 2.5X magnification. That Scheimpflug Dude No, that’s not a bad word. Austrian army Captain Theodor Scheimpflug was determined to get rid of perspective distortion in aerial photographs. Theodor was born in 1865 and got interested in photography in 1902. Theodor combined photography with kites and balloons to make better maps. He read about a British 1901 patent from a French guy named Jules Carpentier. Jules had figured out the solution. Modest as he was, Scheimpflug insisted on giving credit to Jules Carpentier for the details of how to accomplish this distortion removal. Through the vagaries of history, credit for this “principle” was given solely to Scheimpflug. When later questioned about the Scheimpflug Principle based upon his own patent, Jules said he didn’t mind that it was named after Scheimpflug, as long as his invention was found to be useful. Scheimpflug, who got several patents of his own in the realm of aerial photography and panorama cameras with up to 8 lenses, shared his technique freely. Nowadays, most architectural photographers are well-versed in his principle. They can get photos of the fronts of buildings that are dead sharp, even if they’re using a setup with a narrow depth of field. Lots of architectural photographers are now using those Nikon “PC” lenses. But I digress, as I often do. How do we use this PB-4 to get sharp photos of stuff that might not be perfectly aligned with the camera sensor? By using the Scheimpflug Principle, of course. Subject Plane, Optical Center Plane, and Sensor Plane For starters, focus on the middle of your subject without any shift or swing adjustments. To get your rotated subject plane in focus, swing the lens until the red “subject plane”, the orange camera “sensor plane”, and the green “optical center plane” all intersect. In the sample above, the three planes all converge at a spot about 1 meter to the left of the camera (slightly out of the frame). You’re rotating the green plane (the lens), and leaving the other planes alone to achieve this intersection. After the subject plane is in proper focus, you probably need to shift the lens to get your subject centered in the viewfinder. Since the shift movement doesn’t change the direction of the optical center (green line), the subject doesn’t go out of focus while shifting the lens. Scheimpflug Principle In a nutshell, that’s the “Scheimpflug Principle”. Scheimpflug was a smart guy, as was Jules Carpentier. You should thank the both of them. This stuff is a bit complicated, until you go through the alignment exercise yourself a couple of times. It’s a lot simpler to just keep your subject plane parallel to the camera sensor, but where’s the fun in that? Closeup results from setup shown above. Coin face is entirely in focus. The photos above show a coin mounted with a significant rotation, relative to the camera sensor plane. Normally, it would be impossible at these magnifications to get the rotated coin face in focus even when the lens aperture is stopped down. The swing adjustment, combined with the shift adjustment, made getting everything in focus possible with a single photo. It would also be possible to get everything in focus by stacking several photos, where focus is shifted slightly between shots (see discussion below). In the coin detail shot above, the reverse-mounted 60mm Micro Nikkor was stopped down to f/8.0, which gives a pretty shallow depth of focus. Thanks to the swing and shift controls on the PB-4, the coin face is entirely in focus. I didn’t have to stop down to a small aperture, which would have caused resolution-killing diffraction. The vertical field of view here is 9.75mm, or 2.46X magnification. I hope you can tell that this lens yields very, very sharp results. You can get a pretty good idea of the distance to the subject from the lens when using the BR3 ring while mounting the 60mm lens in reverse (using the BR2 ring and step-down rings) by inspecting the overhead gear setup shots included above. The clearance between the light and the subject isn’t huge (about 2 inches), but it’s sufficient to get very good illumination. The whole coin (NOT using the bellows) The coin used in these examples is 39.1mm in diameter. The face itself is 0.55mm offset from the featureless coin surface. This is roughly as close as most people ever get when they use a macro lens by itself. The PB-4 takes you to a whole new level. Since the invention of focus stacking, it’s now possible to get a huge depth of focus via multiple photos (see below). The stacking invention makes Scheimpflug no longer an imperative (unless you use film). It’s still quite nice to get the job done with a single photo, versus combining dozens of shots to get there. Lighting Hardware Example LED ring light mounted onto BR-3 ring It’s often preferable to use a continuous-light source to illuminate small subjects, compared to using a flash. The BR-3 ring works as a nice surface to attach ring lights. There is still enough working range to your subject if you choose a small light. My ring light is about 34mm thick. I like LED lights, because other types of continuous lights tend to cook your subject. Without continuous lighting, the (non-sunlit) subject is usually too dim to focus easily. The light shown above has three tightening screws that grab onto the BR-3 ring. Remote release Infrared remote and 10-pin wired remote Depending upon your camera model, I’d recommend that you use either the cheap ML-L3 infrared release or a 10-pin wired remote to minimize vibrations. Don’t forget to use the electronic front-curtain shutter mode if your camera has it, to really rid vibrations. Working Distance Example subject held in front of lens The shot above shows a diamond ring that is in focus at a medium bellows extension. This should give you a good idea about how much working distance you have between your gear and the subject. There isn't a single "working distance" when discussing a certain lens on a bellows. The higher the magnification, the shorter the working distance. I made a little device that uses an alligator clip to hold small objects. The device fits into the end of the bellows and has the necessary degrees of freedom to raise, shift, and rotate small objects. I don’t know if you can buy any gizmos that will fit into the PB-4 bellows “slide copier” attachment hole for holding stuff. I was forced to make my own; I got tired of having to get my rig close to table tops with tripod legs always in the way. The bottom control knob on the bellows is essentially used to balance all of your gear over the tripod. This collection of hardware can get heavy, so you’ll want to place it at the point of balance after setting the bellows extension. Stacking Software The depth of focus at high magnification isn’t much thicker than a sheet of paper. I recommend that you explore the world of focus-stacking, where you can combine many shots into a single photo. Each shot’s focus is slightly shifted, and the focus-stacking software combines them. The PB-4 bellows is ideal for letting you shift the camera/lens combination on its rack by small amounts between shots to have fine control over the focus shifting. You twist the bottom PB-4 knob to shift the whole camera/lens/light combination without changing magnification. I have an article here where I discuss focus-stacking. The article shows how to use this free software; there are several programs (not free) that accomplish the same task. It generally takes 50 to 70 shots to get enough depth of focus in the final stacked photo. The magnification, lens, and subject will determine how many shots you will need. One downside to photo-stacking is that you will need to crop the final stacked photo, because the edges are ‘fuzzy’. It’s almost as if an ‘FX’ photo ends up being a ‘DX’ photo. Try to allow for a liberal border around your subject by shooting at a lesser magnification. Stacked photo result using CombineZM I used 50 shots to make the finished photo of this wasp. I should have used a few more shots to get the tip of the leaf in full focus. There's about 15mm of focus depth here; without focus stacking, either the leaf or the wasp's eye would be in focus, but not both. I used my LED ring light for illumination. Conclusion I bet you didn’t think using the PB-4 bellows could be this complicated, did you? Close-up photography can get quite involved; think of it as a journey, and not just an end result. There’s a largely unseen world out there, even in your own back yard. Make it visible.