If you didn’t know, the marked f-stop on your lens is probably a lie. The actual light transmission of lenses is almost always less than the marked f-stop. I’m not talking about the lens edges and corners, where transmission is even worse. Real lens light transmission (in the center, at least) is given by its T-stop, where T stands for transmission.   Often, cinema lenses are marketed by their T-stop, because you need to be able to swap lenses and be able to get the same light level at a given f-stop setting. Movie makers and editors are much more demanding than still photographers, it appears. You can still use the marked lens f-stop for determining the depth of focus; it just won't reliably indicate how much light your camera sensor is seeing.   To find out your lens T-stop, you need to either look up the T-stop information on the web, or else you need a ‘reference lens’ with a known transmission for a given f-stop. A really handy website that gives T-stops for many lenses is DxO Mark . This excellent website has much more information than just T-stops, of course.   As an example, I have a ‘reference lens’, which is my Nikkor 85mm f/1.4G AF-S lens. This isn’t actually an f/1.4 lens, but an f/1.6 transmission lens or T 1.6 . DxO Mark website Nikkor 85mm f/1.4G AF-S lens data   As shown above, my 85mm f/1.4 is really an 85mm f/1.6 lens.   If you can’t find a website that has already analyzed your lens for transmission, then you need to figure out the T-stop yourself, starting with a reference lens that you can access.   If you can locate a reference lens with a known T-stop, then you can take a photo of a smooth evenly-lit surface, such as a wall, using your reference lens to establish the exposure. Make sure your camera is in manual mode at a fixed ISO value, where ideally you set the same marked aperture you’ll use on your ‘unknown’ lens under test. Note the shutter speed required for correct exposure.   By the way, you’ll need to switch to ‘spot’ metering, and make sure you are looking at the center of the field of view when metering. Otherwise, the camera meter will be influenced by the (dimmer) edges and corners of nearly every lens. Most camera meters only give you a resolution of 1/3 stop, so don’t expect a more accurate T-stop estimate than that.     For these procedures to work, your camera needs to be able to measure the exposure with the lens aperture actually stopped down to the requested f/stop. My Nikon mirrorless cameras automatically focus and measure the exposure at the requested aperture, and not wide-open (through f/5.6).   Make sure that the tested lens has its focus set to infinity. Lenses get dimmer as you focus closer, and lens T-stops should always be referenced to infinity focus.   If your lens under test doesn’t have the same (marked) widest aperture, then you’ll have to assume that your reference lens has consistent transmission loss at each aperture. Set the reference lens to the same marked aperture as your unknown lens under test, and then note the shutter speed for correct exposure.   Now, switch to your unknown lens at the same marked aperture as your reference lens, and adjust the shutter speed to get the correct exposure. Compare this shutter speed from your shot with the reference lens at the same aperture. This change in shutter speed between lenses can be converted into an E xposure V alue, or EV, to see how much different your tested lens is, compared to your reference lens.    I use a handy website called ScanTips.com . This website has an exposure calculator to convert f-stops into the equivalent EV value. There are many apps available that can do this same thing. To do the math on exposure changes, you need to convert from f-stops into EV values. An EV change of 1 is the same as the change of 1 f-stop. In the calculator ‘A’ side, set your reference lens marked f-stop, shutter speed, and ISO. Also enter your unknown lens marked f-stop, shutter speed, and ISO in the calculator ‘B’ side. This will give you the EV change between lenses. Add this EV change with your reference lens T-stop, and you now have your unknown lens T-stop.   To calculate the Exposure Value (EV) difference between my 85mm marked f/1.4 aperture and its actual f/1.6 T-stop, the calculator was set up like this: EV change from f/1.4 to f/1.6 is 0.33EV   For example, my 85mm lens at the marked f/1.4 aperture had an exposure of 1/1000 second at ISO 400.  My TTArtisan 50mm f/0.95 lens, when set to its marked f/1.4 aperture and ISO 400 also needed a shutter speed of 1/1000 second for the correct exposure.   This means that the TTArtisan f/0.95 lens at f/1.4 would also be T-1.6, having the same transmission as the Nikkor 85mm f/1.4 lens at the same marked f/1.4 aperture.   I set the TTArtisan 50mm lens to a marked f/1.0 (one stop wider than f/1.4), and the camera meter indicated it needed a shutter of 1/1600s. TTArtisan 50mm f/0.95 lens at f/1.0   The results above indicate that a change from f/1.4 and 1/1000s to f/1.0 and 1/1600s means that the TTArtisan lost another 0.33 stops of light transmission. I was expecting the correct exposure to be 1/2000s at f/1.0.  When I then changed to the marked f/0.95 aperture, the meter indicated correct exposure needed a shutter speed of 1/2000s.   Since this TTArtisan wide-open at f/0.95 transmits twice the light of my 85mm Nikkor wide-open, that means that its T-stop would then be T 1.1 , which is 1 stop faster than the Nikkor 85mm’s T 1.6 .   I guess this lens loses some of its bragging rights, going from “f/0.95” to the actual transmission of T 1.1.

If you need to focus-stack a dozen or fewer photos quickly and easily, consider using the ON1 Photo Raw  editor. I’m using the 2023 version of ON1  in this article.   If, on the other hand, you want to stack scores of shots with the most capable available software, you probably want to take a look at Helicon Focus. Here’s a link to an article I made on using Helicon Focus . I often find myself trying out ON1  with a set of stacked shots, since it’s so easy to use. If I like the results, I’m done. If I don’t like the results, then I switch over to Helicon Focus  to get the job done. Select your shots to stack   The first step is to select the photos that you want to stack. It’s critical that your shots have good focus overlap, or the stacking will either fail or look awful. It’s generally okay if you hand-hold the camera, since ON1 can handle misalignment. Cameras that have a focus-stacking feature work much better for getting correct focus overlaps, but you can also make stacks with manual focus.   If you select too many shots to stack, ON1  won’t let you select the “Focus” option until you decrease your selection total. Generally, it won’t let me select more than 14 shots. The ‘Focus Stacking’ dialog   As shown above, you will get the Focus Stacking  dialog to appear after clicking the ‘ Focus ’ icon. You might not get all of your selected shots to be automatically used in the stack. I used a manual-focus lens in the above stack, and the software de-selected some shots with improper focus overlap.   I always leave the Align Photos  selected, since properly-aligned photos will still work, too. Some ugly image artifacts     If you don’t have a proper focus overlap between all of your shots, you’ll probably notice that not every shot gets selected at the bottom of the dialog. You can re-enable these shots in the stack, and look for potential image artifacts showing up in the stacked shot.   You can un-select shots at the bottom of the dialog (check marks) until you make the unwanted artifacts disappear. Artifacts are gone after de-selecting some shots   The stack above was actually hand-held, showing how well the auto-align feature can work. I think I had some front-back sway issues while photographing the stack, causing some incorrect focus overlaps; this is why not all of the shots worked properly in the stack. I used a focus-stacking camera for the above shots, but the viewfinder blacks out during the shooting and holding steady is a challenge.   This ON1  stacking isn’t suitable for most macro subjects that require huge numbers of frames to overcome paper-thin depth of focus. It’s much more suitable for things like landscapes or product shots at more normal distances where a dozen or less images will cover the scene.     ON1 and Helicon Focus Compared Stack 10 shots with Helicon Focus Stack 10 shots with ON1   If you look closely in the above pair of shots, you can see that Helicon Focus  is a more refined product than ON1 . There are several small rough spots which I’ve pointed out in the ON1  stack that are absent from the Helicon Focus  version.   You’ll find yourself having to use tools like the healing brush to smooth over little defects in ON1  focus stacks.   On the other hand, Helicon Focus  cropped a bit more than ON1  and seems to have made a different decision on what to use for the most out-of-focus background.   Helicon Focus  is more adept at handling hand-held stacks and compensating for camera movement than ON1 , as well.   The white balance is different with Helicon Focus , but that’s easily adjusted after stacking by using other editors.   There are some raw-format photos that Helicon Focus  can’t use, but you can easily convert them into DNG format using the free Adobe DNG Converter  and then stack this form of raw files.       Summary   If I had to choose, I’d stick with Helicon Focus  over using ON1  for focus stacking. ON1  is the simplest and fastest program to use, but it’s definitely more limited in capability and finesse.

I already did an article on the technical aspects of doing panorama photography. It discussed ways that you can figure out the pivot location for your lens (at the lens entrance pupil) to totally eliminate parallax error. That article is located here   What I haven’t yet discussed is the best way to actually support your camera/lens on a tripod. Photographers generally know about using Arca-Swiss supports, but most of those designs are completely incompatible with doing correct panoramas or weight balance. I’m going to address those issues, and show you how you can have the best of both worlds.   A really nice aspect of the hardware I’m going to discuss is that you can buy this stuff for really cheap. Or you can buy really expensive stuff, if that’s your thing.   I’m not trying to sell anything, so any mention of specific hardware doesn’t mean that it’s necessarily better than some other hardware.  An important consideration, however, is the length or adjustability range of some clamps or plates.   Camera “L” brackets are a great way to mount your camera onto an Arca-Swiss mount, but how do you shift them away from the tripod pivot axis for a proper panorama? There’s a way. Enter the ‘ nodal slide ’. This device was designed to let you move the camera away from the tripod centerline along the lens axis. It uses Arca-Swiss hardware, so it’s adjustable, fast, and secure. A ‘Nodal Slide’ top view   The hardware shown above is a combination of an Arca-Swiss plate with an Arca-Swiss clamp at one end. The clamp is perpendicular to the plate, so that a camera with an Arca-Swiss plate attached to its base will then mount perpendicular to the long plate. The entire rig is then attached to another Arca-Swiss clamp on the tripod head.   There’s a handy bubble level on the slide. It’s very important to get your camera level when making panorama or architectural shots. A ‘Nodal Slide’ bottom view   In this bottom view, you can see a stainless ¼-20 screw that can be used to attach your camera to the slide, if the camera doesn’t have an Arca-Swiss plate on it. Normally, this screw will go unused but can be left in-place. A ‘Nodal Slide’ side view   The slide has a millimeter scale on both sides, which is crucial to allow quick repeatable mounting of the camera/lens at its proper entrance pupil location over the tripod pivot point. Camera with an ‘L’ bracket for Arca-Swiss mounting   The ‘L’ bracket shown allows the camera to get clamped in either the landscape or portrait orientation onto the nodal slide. This bracket is just the right length to allow free access to the camera’s battery compartment on its base.   Be careful to align the lens axis over the center of the tripod rotation axis before clamping the camera onto the nodal slide. Shift Along the Lens Axis Camera with its lens entrance pupil over the tripod pivot   Some lenses have really, really long separations between the camera sensor and the lens entrance pupil (nodal point). If you buy ‘short’ plates or clamps, you might be limiting yourself in a way that you could later regret. On the other hand, hardware with a huge adjustability range can rapidly get unwieldy in the field. You’ll have to decide on what’s a happy medium for yourself.   Beware of trying the kind of offset shown above with a tripod “ball head”. Most ball heads aren’t strong enough to cope with off-balance loads like this. You need a strong tripod head and a strong tripod, too. Camera in portrait orientation using its ‘L’ bracket   Most photographers prefer taking their panorama shots in portrait orientation. This hardware permits that orientation, while still being able to rotate about the lens entrance pupil centered over the tripod pivot point. Make sure that the camera ‘L’ bracket is tightened properly onto your camera, so that it doesn’t slip while in portrait orientation with a long, heavy lens attached.   There are zillions of rotating “panorama heads” for tripods that totally miss the point of how correct panoramas are achieved.  These heads expect you to attach them to the camera body tripod screw and then pivot about the camera body; they don’t know anything about lens entrance pupils or how to get rid of parallax error.   The hardware shown is quick to attach/detach and very solid in use. It is also easily adjusted.   It’s wise to try to get the balance point of your camera/lens centered over your tripod center column when doing ordinary single-shot photography. This will help minimize vibrations and is the best technique to ensure your tripod doesn’t tip over with your heavy gear on it. This hardware enables you to balance your setup quite easily.   I recorded pictures on my cell phone showing the correct lens entrance pupil mounting for each of my lenses at the focal lengths I might use. This makes it easy in the field to look up a correct setup, where I just need to match the nodal slide’s millimeter scale adjustment to the saved photo on my phone. It’s too hard for me to memorize these settings. A panorama that stitches perfectly The panorama above was created by sliding the camera on the nodal slide to get the pivot point of the tripod just underneath the lens entrance pupil. The shots making up the panorama stitched together to make a perfectly seamless panorama, using Capture One . Shift the Camera Side-to-Side Shift your camera left/right on its Arca-Swiss plate   The nodal slide is also very helpful in macro work for a couple of reasons. You can easily slide your camera/lens forward and backward without moving the tripod for careful close-up positioning. You can also easily shift your camera side-to-side and create a macro panorama from multiple shots. 3D anaglyph using shift (get out your red/blue glasses)   This hardware is also handy for making 3D anaglyphs by shifting your camera left/right on its Arca-Swiss plate. I used the Zoner Photo Studio to make the anaglyph here. You’ll usually want to shift by about 3 inches or 8 cm between shots, since that is roughly your eye separation distance.  If you’re really far away from the subject, shift by more than this. For macro subjects, smaller shifts should be used (around 3mm).   If you just search for ‘nodal slide rail’ at sites like Amazon, you’ll get a plethora of hardware results to select from. Keep in mind that it’s assumed you already have an Arca-Swiss compatible L-bracket or plate on your camera. You’ll also need an Arca-Swiss clamp on your tripod head.

Believe it or not, this lens is still for sale as of this writing. This lens was introduced way back in 2010. I was given this Nikkor by my father many years ago, and I never really gave it much use or did a thorough evaluation. That’s my loss; this lens is much  better than I assumed it was. This lens was designed to be used in combination with their 18-55 DX kit lens for a huge zoom range.   Having a fairly dim aperture, it’s very sluggish when mounted on my DSLRs when compared to my ‘pro’ lenses. Low lighting levels are quite problematic for accurate focus, or even focus at all. When I mounted this lens on my mirrorless Nikon Z9, however, there was a world of difference. For typical photographic subjects, it’s now more than capable (not recommended for birds flying straight at you, however).   The 55-300 is extremely light for its focal length range. Compared to my ‘pro’ telephotos, it almost feels like I forgot to mount a lens on my camera.   Keep in mind that this zoom costs about 9% of what my Nikon 500mm f/5.6 PF cost me, or roughly the sales tax. I used to think that the 500mm was pretty light, but it weighs almost triple what this zoom weighs. On my more difficult hikes, I know which one I’d rather haul along.   In DX mode, the Z9 provides a little over 19MP images with this lens. For most subjects, this is plenty. You’ll have to decide for yourself if that level of resolution is acceptable or not. 55-300 at 300mm on Nikon Z9 using the FTZ II adapter   General lens specifications   Dimensions: 76.5mm x 123mm (3” x 4.8”) at 55mm infinity focus, 184mm at 300mm while at minimum focus of 1.4m (4.59 feet).   Weight: 580 grams, 18.6 ounces.   17 elements, with 2 ED, 1 High-Refractive-Index.   Metal mount, with rubber mount seal. Otherwise unsealed lens.   9 rounded aperture blades, with f/22 to f/29 minimum aperture.   HB-57 snap-on lens hood.   58mm plastic filter threads (rotates during focus)   0.28X maximum reproduction ratio claimed (see below).   Polycarbonate lens body.   VR-II claimed 4 stops, with a tripod-sensing feature.     Irritating lens characteristics   Manual focus is only  possible when lens switch is at ‘M’. Some lens body wiggle when zoomed out (focus unaffected). Manual-Focus ring , filters, and hood rotate during autofocus. Very skinny manual focus ring (1/4 inch) at lens front. Zoom ring and focus ring rotation range both only 90-degrees. Sluggish autofocus during large focus distance changes. Lateral chromatic aberration (purple fringing) Ridiculously far minimum focus distance at 55mm zoom. Lens at 55mm zoom Lens at 300mm zoom     Vignette Worst vignette at 55mm (left) and 300mm (right)     Vignette is generally ignorable, to my surprise. I often have to increase it with my photo editor, for aesthetic reasons.     Lateral Chromatic Aberration Lateral chromatic aberration 55mm (left) 300mm (right)   Purple fringing is there, so you’ll need to correct this using your favorite photo editor in high-contrast shots. The worst I measured was 8.3 microns, which is (8.3/4.35)= 1.9 pixels at 300mm with this Nikon Z9 sensor. The Z9 has 4.35 micron pixels. Lateral chromatic aberration, 55mm f/4.5   The shot above shows the uncorrected purple fringing with the tree branches over the blue sky. Not terrible, but it’s there.         Longitudinal Chromatic Aberration LoCA at 72mm f/4.5 Red (left), Green (mid), Blue (right)   Longitudinal chromatic aberration (LoCA) hasn’t been an issue in the photos I’ve taken. I have expensive lenses that have much worse LoCA than this lens. The measurements show that red is focused farthest from the camera sensor, and green is the nearest.     Distortion   There is only a slight hint of barrel distortion at 55mm, which gradually turns into pincushion distortion at the longer focal lengths. 300mm pincushion (left), removed (right) in editor   The most severe distortion is at 300mm, and even then it’s pretty slight. As shown above, I completely removed the distortion using Lightroom  with its lens profile from Adobe.   Focus   With sunny conditions, you shouldn’t have any complaints about focus. In dimmer light, focus is heavily dependent upon your camera. The AF-S motor in this lens is just plain weak, so you need to be somewhat close to the right subject distance to nail focus with a decent response time. With my DSLRs, focus-hunting is the norm in shade. With my mirrorless Z cameras, focus is quite responsive in fairly dim light as long as the subject doesn’t start out being extremely out of focus.   This is definitely not  a pro lens in regards to focus speed.   As mentioned above, this lens has no manual-focus override, so you have to put the lens switch on “M” to use the focus ring. Very clunky.   Close Focus   This lens actually focuses closer than Nikon’s specifications. At 55mm, it focuses down to 1.275m (4.18 feet) instead of 1.4meters.   At 300mm, it focuses down to 1.32m or 4.33 feet from the camera sensor. At this setting, the field of view is just 3 inches (76.2mm). For a DX sensor, that means it can achieve 0.315X magnification. The working distance (from the front of the lens) is 1.14meters (without the snap-on lens hood).   Bokeh 180mm f/8 bokeh example   The bokeh shows a minor fringe around the light blob edges. It’s not great, but I’ve seen much worse than this on other lenses. 9 rounded aperture blades really help.   Focus breathing   There is almost no  change in focal length as the focus distance is changed (focus breathing). It’s really common to reduce focal length as focus distance is reduced, and it’s nice to see that this lens doesn’t show this.     Actual focal length   I measured the actual focal length at 300mm to be 292mm. This is better than most zooms. My Sigma 150-600 zoom, for instance, is actually 285mm at the 300mm setting.     Parfocal   This lens is nearly parfocal, but not quite perfect. Focus changes very little as you zoom. Keep in mind that the aperture isn’t very bright, so this would somewhat mask any focus changes.     Infrared Lenses with this many elements are supposed to be horrible with infrared. I tried out my Nikon D7000 that was converted into 590nm infrared (including an infrared anti-reflection sensor cover) by Kolari Vision. I’d say the results are pretty good. Vignetting is a little stronger in infrared light, but that’s easy to compensate for with an editor, if desired. 590nm is orange light, so orange and red are visible in addition to infrared.   The 850nm sample shot below was with an added IR filter. There’s no color left at this long IR wavelength. Illumination looks pretty even, with no dreaded central hotspot. 135mm f/5.6 590nm infrared 135mm f/8.0 850nm infrared   Resolution   I have always maintained that photos start looking ‘acceptable’ when the resolution MTF50 measurements get above about 30 lp/mm . After resolving above 40 lp/mm , image cropping starts to become viable.   I have been very pleased with this lens, even at its worst resolution setting of 300mm f/5.6. I have included shots in this article below that let you be the judge. Talk is cheap.   I stopped taking measurements after f/16, because diffraction totally kills the resolution.  The lens edge resolution isn’t anything to write home about, but it improves when zoomed beyond about 70mm. Overall resolution is really good until about 240mm, and goes downhill from there.   I only use unsharpened raw-format files for the resolution analysis. Any form of file sharpening would falsify the results. These files were all produced with the Nikon Z9 camera in DX mode. MTF50 lp/mm peak resolution at 55mm and 70mm MTF50 lp/mm peak resolution at 100mm and 135mm MTF50 lp/mm peak resolution at 200mm and 300mm Samples 300mm f/5.6 with Nikon Z9 and bird subject detection 300mm f/5.6 with vignette added using Capture One 300mm f/5.6 300mm f/5.6 with added vignette 300mm f/8 140mm f/5.0 210mm f/5.3 210mm f/8.0 55mm f/8.0 78mm f/8 used Silver Efex Pro     A huge thankyou to Frans van den Bergh for his MTFMapper   program to analyze the lens.

There are two kinds of chromatic aberration. The aberration most photographers are familiar with is called lateral chromatic aberration, and that’s what causes those purple smears near the edges of the frame (such as around tree branches against the sky). Most photo editors can reduce or eliminate this defect.   This article is about longitudinal chromatic aberration ( LoCA ), which is caused when a lens focuses different colors of light at different distances along the lens axis. This aberration is mostly noticed by seeing bright out-of-focus subject highlights take on different colors in front of and behind the focus plane. The effects of this aberration are roughly the same all across the camera sensor. Very few photo editors can fix this defect. LoCA picture thanks to the Wikipedia site Near (in-focus) light: reddish fringes, far light: greenish fringes   The lights above show some color fringes due to LoCA. It’s not horrible, but you can tell it exists. The picture was shot with my Nikkor 85mm f/1.4 AF-S at f/1.4. This is a crop from a pixel-level magnification.     I used the MTFMapper program by Frans van den Bergh to perform the analysis. He provides files that you can print out, including a couple of special “focus position” charts. To shoot the focus chart, I had to set up my camera at 45 degrees to the chart, with the ‘short’ slanted-line targets nearest the camera. The chart is designed so that the natural perspective distortion will make the slanted targets look like the same height when the short slanted targets are nearer to the camera than the tall slanted targets. Frans provides two styles of focus position charts; here, I chose the chart with a single row of heavy slanted lines.   When photographing a ‘focus position’ chart, it’s not critical that you nail focus in the center of the chart to analyze LoCA. It’s only the relative peak focus between the red, green, and blue channels that’s important.   In the program Settings|Preferences , I set the ‘ Threshold ’ value to 2.0 and I set the Bayer color channel to red , green , and finally blue  in three separate analysis runs of the Focus Position chart. I used raw-format photos of the focus chart. The MTFMapper  program doesn’t yet understand my Nikon Z9 ‘HE’ format, since it uses LibRaw . I have to convert them into DNG format using Adobe’s free converter. Set Threshold and Bayer channel then Open images     For the tests, I used both my Nikkor 85mm f/1.4 AF-S and my TTArtisan 50mm f/0.95 lens on my Nikon Z9 camera. I picked these lenses, because I know that they have noticeable longitudinal chromatic aberration (LoCA). Later, I'll compare them to a lens with very little LoCA.   I photographed the chart at a few different apertures, to see how the aperture would affect the LoCA. TTArtisan 50mm at f/0.95 R,G,B Bayer channels   The TTArtisan 50mm f/0.95 lens shows the red Bayer channel focusing farther from the camera (left) than the green and blue channels. The plots are shown with R then G then B left-to-right. The same TTArtisan 50mm stopped down to f/1.4 again shows the red channel focusing farthest from the camera. The green and blue channels are about the same. TTArtisan 50mm at f/2.8 R,G,B Bayer channels   At f/2.8, the TTArtisan shows the same focus shift pattern as the other apertures. The plots are shown with R then G then B left-to-right. The focus separation between red and green here is 15.7mm.   The focus separation distances depend upon the chart size. If you stick with the same chart, you can directly compare different lenses. TTArtisan 50mm at f/2.8 red channel close up   When I zoom in on the plot, you can see that the actual focus offset from the vertical dashed line is provided (-21.1mm here). It also includes the peak MTF50 resolution (0.197 cycles per pixel here). Nikkor 85mm f/1.4 at f/2.8 R,G,B Bayer channels   The Nikkor 85mm f/1.4 lens tests showed very  similar behavior to the TTArtisan 50mm lens at the equivalent apertures. The f/2.8 plots above, for example, are a near twin to the TTArtisan plots at f/2.8. The focus separation between red and green here is 17.8mm, versus the TTArtisan’s 15.7mm at the same aperture.   Looking at the red channel focus peak, it’s significantly farther away from the camera than the blue and green channels. This is classic longitudinal chromatic aberration.   The aperture setting has very little effect on the LoCA of either lens. No channel (luminance), 85mm f/1.4 lens at f/2.8   When no  color channel is selected in the Preferences , the plot looks about the same as the ‘Green’ channel does. This is effectively what the camera is using for focus. Nikkor 24-120 f/4 S at 85mm f/4 Red and Green channels   Shown above is a lens with very little LoCA. The focus separation between red and green here is only 4.8mm.   Many thanks to Frans van den Bergh for his terrific MTFMapper program. It’s very effective for showing how a lens focuses different colors at different distances.

I was comparing a DSLR (the D850) against a mirrorless Nikon Z8 using the same lens. After careful autofocus fine-tune adjustments, I was able to improve the focus results for the D850 camera. Since both cameras have the same sensor resolution, the Z8 (or Z9) should be able to achieve at least the equivalent focus accuracy (e.g. equal lens resolution measurements) of the D850.   I have never messed with the autofocus fine-tune feature on either my Z8 or Z9. I have read that it’s completely unnecessary, and until now I had believed this narrative. It now seemed like an appropriate time to go there. All of the testing and measurement associated with focus calibration isn’t exactly enjoyable, but there’s no way I was going to let my D850 beat my Z8 or Z9 without a fight.   I should mention that I used AF-C with 3D-tracking focus on both cameras. This is my favorite focus mode, so it’s how I like to test my lenses for real-world resolution results. The best way to determine the highest resolution a lens can get is to forget focusing the lens entirely, and instead move the camera/lens combination on an adjustable rail in small (sub-millimeter) amounts between test shots. But that's not how photographers actually shoot. Focus Fine-tune in the Nikon Z8 Setup Menu   By default, the Nikon Z camera autofocus fine-tuning is turned off. The fine-tuning features are located in the Setup  menu. AF fine-tuning menu   To adjust the (attached) lens, scroll down to the “ Fine-tune and save lens ” option. Set the desired setting   As shown above, I set the 500mm f/5.6 PF fine-tune value to -2 , which will then force the lens to focus slightly nearer to the camera. Press “ OK ” to save the new setting. The Nikon D850 resolution testing results   As shown above, my Nikon D850 was focus fine-tuned to -2 when I conducted focus testing. Many of the resolution readings hovered around MTF50 80 lp/mm for the center of this Nikkor 500mm f/5.6 PF lens. This was the best that I was able to get out of that camera/lens combination. I use the free MTFMapper program to measure lens resolution.   By the way, the horizontal axis values above are just the frame number of each shot.   The data plotted above had an average MTF50 resolution of 71.7 lp/mm, with a peak of 84.8 lp/mm and a standard deviation of 10.3.  Notice that many of the resolution readings hovered around 80 lp/mm.   There’s a huge spread of resolution results, which means that the camera was quite variable in how it focused on the resolution target. This is unfortunately completely normal for a DSLR using phase-detect focus. This spread (variation) of resolution results is reflected in the standard deviation value of 10.3. The Nikon Z8 resolution testing results   My Nikon Z8 testing results (with NO AF-tune adjustments) are shown above. Their consistency is superior to the D850, but many of the resolution readings seem a bit lower than what the D850 had occasionally achieved.   The Z8 resolution testing results had an average MTF50 resolution of 74, with a peak of 98.2 and a standard deviation of 6.7.    While the Z8 on average  got better resolution than the D850, it looked like there was room for improvement. I tried various AF-tune values on the Z8, and it turns out that the same  AF-tune value of -2 got the best results out of this lens. Normally, different cameras will have very different fine-tune settings with the same lens. The Nikon Z8 resolution testing results with AF tune -2   The resolution results from the data plotted above got an average MTF50 resolution of 77.1. The peak reading was 84.1, with a standard deviation of 5.3.   Although not huge, the lens resolution increased from an average of 74 to 77.1 lp/mm after implementing the fine-tune compensation.   Note that the D850 standard deviation was 10.3, while the Nikon Z8 standard deviation was 5.3.  This demonstrates significantly less focus variation with the mirrorless camera.   A word of caution is in order. Don’t  use ‘pinpoint’ or ‘starlight’ focus mode when investigating autofocus fine-tune. These two modes use contrast-detect instead of phase-detect, and therefore ignore the fine-tune calibration. If your target is quite small, you might want to use the single-point focus mode, which is very selective and still uses phase-detect and allows AF-C focus.   Another caution: if you’re using F-mount lenses and you have more than one FTZ adapter, you’ll have to pay attention to which adapter is in use. Teleconverters can also mess up the fine-tune calibration.   The Nyquist Limit   According to Edmund Optics , the absolute limiting resolution of a sensor is the Nyquist Limit which is half of the sampling frequency (pixels/mm). For the Nikon Z9/Z8, for instance, the Nyquist limit is (8280/35.9)/2 pixels per millimeter (231/2 pix/mm) horizontal or (5520/23.9)/2 pixels/mm vertical, or again (231/2) pix/mm.    The Nyquist limit of (231/2) lp/mm is then 115.5 lp/mm.    The typical actual frequency response includes what’s called the “Kell Factor” named after Raymond Kell, which is conservatively set to 0.7.  This value helps compensate for the physical space between the light-sensitive portions of the pixels, and to avoid patterns similar to the moire effect. This means the practical actual sensor frequency response limit is now (115.5 * 0.7) or 80.85 lp/mm.     Given this information, any measured resolution above 80.85 lp/mm is unreliable. In any event, the Z8 average of 77.1 lp/mm with this 500mm f/5.6 PF Nikkor is darned near the Nyquist limit.     Summary   It turns out that Nikon included the AF-tune feature in their Z cameras for good reason. It’s not useless and ignorable after all. I was able to squeeze out a little bit better focus accuracy (and resolution) from my lens. The resolution increase was only about 4 percent, but I’ll take it.   The Nikon Z8 won the focus fight over the D850 after all. It’s no longer feeling embarrassed by the D850.

I have read on several occasions that you should always turn off IBIS ( i n- b ody i mage s tabilization) when you use a tripod. I’m such a terminal skeptic that I decided to try it for myself.   For my tests, I decided to pick on my Nikon Z9 and the 24-120 f/4 S Nikkor lens at 120mm and f/4. This lens doesn’t have any internal vibration reduction, and instead it entirely relies on the camera IBIS system.   I used a wired remote release and my heaviest tripod and on top of a concrete/porcelain tile floor indoors, so that any other kind of vibrations should be minimal. I got about 3 meters from my target, which is the edge of a tiny razor blade.   I picked a fairly slow (1/30 second) shutter speed, which should in theory readily show image motion (if there is any).   The Nikon Z9 (and Z8) have pure electronic shutters, plus they focus at the shooting aperture (through f/5.6). This means that these tests won’t be affected at all by ‘shutter-shock’ or moving aperture blades.   I used my MTFMapper program to evaluate the image resolution, which is much, much more sensitive than the naked eye in seeing any sharpness loss from vibrations.   I should mention that the orientation of the edge being evaluated will change the measured resolution. Every combination of sagittal and meridional direction will give a different result, which is big reason why it’s impossible to give a single-number answer to overall lens resolution.   I re-focused the lens (AF-S mode) using pinpoint focus mode in between each shot. This means that there should be a small variation in resolution between each test shot, due to the focus distance natural variation.   The target (edge) was far enough away that I did my measurements on just a 226-pixel portion of the razor blade. The whole point in this setup was to give the IBIS system the maximum chance to mess up the sharpness. Extreme crop of frame showing the target selection (in cyan) The whole frame Spreadsheet of resolution results     Taking 20 shots with and then without camera IBIS active, I plotted the resolution results and got the average and standard deviation of the MTF50 resolution, in lp/mm units.   The average resolution using IBIS was 95.5 lp/mm. With IBIS turned off, the average was 94.1 lp/mm. The data spread (standard deviation) for active IBIS was 1.82 versus 2.55 without IBIS.   In other words, there’s hardly any difference when using IBIS or not, when mounted on the tripod. If anything, there is a slight improvement using IBIS. This is the exact opposite of what I’ve been reading on the internet.   It’s possible, of course, that the effect of using IBIS might be highly dependent upon which camera model you use. I only know that my Nikon Z9 and Z8 cameras use the exact same IBIS system.   Since it’s a pain to mess with switching IBIS on/off in different situations, I’m glad to know that you needn’t bother with turning IBIS off when mounting these cameras to a tripod.

The highest frequency you can accurately capture in a photo is called the Nyquist frequency, no matter how good your lens is. If you take a picture of finely-spaced details that are smaller than twice your camera sensor’s pixel spacing, you’ll get that ugly aliasing. In other words, your sensor needs at least two pixels across for every skinny line in a light-dark pattern to properly record them.   Aliasing is often called ‘false detail’. With this defect, you can get weird color rainbows where none exist and also light/dark patterns where there shouldn’t be any.   In the past, the only way to get rid of aliasing was to either buy a camera with more pixels or to fuzz-out the image using a camera that had an anti-aliasing sensor filter. Neither option is very good, unless you have plenty of disposable income for that huge medium-format camera.   Several camera companies, now including Nikon, let you perform pixel-shift shooting. With this technology, your camera can rapidly move (shift) your camera sensor by typically half or a full pixel width both horizontally and vertically. After moving the sensor, the camera takes another photo and then repeats the process with each neighboring pixel. After the fact, you can use an editor to combine these shots into a single photograph that has effectively more pixels in it.   If you haven’t already figured it out, this means that you can’t use pixel-shift shooting for moving targets.   The Nikon Z8 (plus the Nikon Zf and Z6III) support pixel-shift shooting. You can take 4,8,16 or 32 shots and then combine them using Nikon’s NX Studio .  I made an article about how this process works located here .    You can now get pictures with up to 16512 X 11008 pixels, or 181MP , if you choose the 16 or 32-shot options. I noted that the combined shots are 912MB (in NEFX form). I shoot in the raw ‘HE’ format, to get smaller raw files. When I used the free Adobe DNG Converter, these shots were reduced to 559MB. Still huge.   Everybody talks about the pixel-shift shooting benefits of higher resolution and image noise reduction, but the ability to reduce or eliminate aliasing has been largely ignored. 70mm 1/320s f/4 ISO 5000, 200% zoom view, single shot   The shot above was taken from the 1st capture out of the 32-shot sequence that created a pixel-shifted picture. I shot at a distance that clearly shows aliasing (see the barcode above). It’s easy to see the blue and orange colors inside the barcode that didn’t exist in real life. The screen capture here is at 200% zoom from a much larger image.   As an aside, note that there’s a fair amount of image noise and much of the text is illegible. I did a 32-shot pixel-shift sequence to show the limits of what this camera could do to rid noise, increase resolution, and of course attempt to rid aliasing. 70mm 1/320s f/4 ISO 5000, 100% zoom view, merged 32-shot   The merged 32 pixel-shifted shots make a world of difference. Besides the obvious resolution increase and image noise elimination, note that the barcode was transformed from false orange/blue mush into distinct lines. Horrible aliasing and noise, single shot NO aliasing and no noise, 32-shot pixel-shift merge.   As seen above, the standard Nikon Z8 sensor resolution resulted in a shot where black lines in the barcode were replaced by fake orange and blue rainbows. This effect can really make some fabrics look horrific, too.   All of the shots shown were processed in Capture One 2023  with no sharpening or noise reduction. If I were to process the merged shot with my Topaz DeNoise AI , it could be made even sharper than what you see here.   I used my Sigma Sports 70-200 f/2.8 zoom for all of the shots in this article. This is a really sharp lens, and it’s obviously capable of producing much higher resolution than my Z8 sensor can use. If you notice that your photographs have aliasing in them, it’s a dead giveaway that your lens resolution is better than your camera sensor.   As you can see, going from a sensor with 5520 X 8280 pixels to an effective sensor with 11008 X 16512 pixels is an enormous jump in quality that has to be seen to be appreciated. It’s just a shame that you can’t do this with action shots.   While it’s impossible to rid aliasing in all situations, this technique will get rid of it for the vast majority of cases.   I’m still waiting somewhat impatiently for this feature to show up on my Nikon Z9 with the next firmware update…

When you shoot multiple shots to stitch into a panorama, you should pivot the lens around what’s often called the entrance pupil . This magical pivot spot is the only  location that will eliminate parallax error. This spot is also known as the nodal point .   If you don’t pivot your lens in the correct location, you’ll end up with overlapping shots that don’t match up precisely. Stitching programs try to compensate for this error, but it’s better to get the right shots in the first place.   Unfortunately, lens manufacturers don’t normally provide the information about the lens’ entrance pupil. In this case, you’ll probably have to figure it out for yourself. Believe it or not, sometimes the entrance pupil can be located outside  of your lens.   To set up a lens for proper panorama shooting, you’ll need a tripod head that can rotate about the vertical axis, and you’ll also probably need an attachment plate that you use to offset the camera tripod screw from the tripod’s pivot axis. The best attachment plates are Arca-Swiss (your tripod head needs to have an Arca-Swiss clamp). With these plates, you can easily slide the camera/lens and then securely clamp them in place.   There are also special ‘panorama heads’ you can buy to make panoramas, instead of the more generic Arca-Swiss clamps. You still need to locate the pivot-point(s) for your lens to make proper use of them, however. Beware that zoom lenses have a different pivot point for each focal length. Camera attached to a long Arca-Swiss plate   In the photo above, the camera is attached to a long Arca-Swiss plate on top of a tripod. The long plate allows the camera to be shifted far from the tripod rotation centerline. Now, when the tripod head gets rotated the camera/lens will rotate around the vertical red line instead of the camera tripod socket.   Usually, really long Arca-Swiss plates are a pain and are best avoided. Here’s a case, however, where a long plate is exactly what’s needed. As you’ll see below, sometimes even the hardware shown above isn’t enough to achieve a correct pivot.   Method 1 to Locate Pivot Location   To gather the information about the ideal pivot location, you need to start by taking photos with subjects at medium and long distances that are aligned with each other. Start by aligning the near and far objects in the exact frame center. Your camera should be perfectly level. Now, rotate the tripod head to get those objects on the left-hand side of the frame. Take a shot with the distant detail on the left frame edge and then rotate on the tripod to the right edge of the frame and take another photo.   Repeat the process, but first shift the camera/lens combination in the tripod’s Arca-Swiss clamp by a large amount. Make notes about which shift location was used for each pair of shots.   With a mirrorless camera, you might get away with just switching to a magnified view to check for left/right alignment and skip having to review photos. The first attempt: pivot around the camera tripod socket   I used an 8-meter-away window frame for the medium object, and a 500-meter-away palm tree for the distant object. I adjusted the camera position until the medium and far objects were right next to each other in the exact frame center.   Next, I pivoted the camera to place those objects on the left side of the frame. I captured the first shot. Close object aligned with distant detail on the frame left edge Distant detail appears shifted right  from the window frame       Next, I pivoted the camera to place those objects on the right side of the frame and took another shot. Close object aligned with distant detail on the frame right edge Distant detail appears shifted left  from the window frame   The results from pivoting over the camera’s tripod socket were terrible. The distant object shifted severely, compared to the window frame. It slid from one side of the window to the other, just by photographing it from opposite sides of the frame.   What’s shown above is classic parallax error. The distant object keeps moving, relative to a closer object, when shot from different left-right locations in the frame. The next test: pivot around the lens as shown     Since I am using a mirrorless camera for the testing, it’s pretty straightforward to just iterate as follows, once I have my near/far objects aligned in the frame center using a magnified viewfinder image:   1)    Pan left or right and observe any shifting of the far object. 2)   Slide the camera/lens forward or backward in the Arca-Swiss clamp by maybe 10mm and lock it down. 3)   Repeat the panning to see if the far object shifting error grows or shrinks. If it is growing, then slide the opposite direction in the clamp. Go to step (1).   In my testing, the trends indicated that moving the pivot point more toward the lens front got better and better results. Finally, I ended up with the configuration shown above. The entrance pupil is roughly between 90 and 100mm from the camera sensor at the 24mm focal length. I couldn’t tell the difference after I got to within a zone of maybe 5mm at this focal length. Close object aligned with distant detail on the frame left Distant left-detail appears the same as in the frame center!   Close object aligned with distant detail on the frame right Distant right-detail location matches the frame center and left!     After I located the proper lens pivot location, I attached the Arca-Swiss plate onto the camera such that one end of the plate exactly aligned with the Arca-Swiss tripod clamp edge. This makes it easy to reliably place the camera onto the tripod with perfect alignment for correct panorama pivots.   I got lucky with this 150mm Arca-Swiss plate. If it were any shorter, then I wouldn’t be able to quite reach the lens nodal point with the plate fully gripped inside the tripod head’s clamp.   The top photograph shows the correct nodal point (entrance pupil) for the Nikkor 24-120mm f/4 S lens when zoomed to 24mm. Same lens zoomed to 120mm: entrance pupil now located at 59.5mm I got my smug smile wiped right off of my mouth when I now tried zooming the lens from 24mm out to 120mm. Big-time parallax error had returned. After repeating the panning procedures at this zoom setting, the new nodal point was located as shown above. Method 2 to Locate Pivot Location   The following technique can at least get you close to finding the lens nodal point (entrance pupil). This technique is more challenging and time-consuming than the first method.   You need to draw the lens horizontal field of view (FOV) angle on paper, with a line splitting that angle exactly in half. In the case of this 24mm setting, that’s 73.7 degrees, with the split line at 36.84 degrees. Use a protractor to measure the angle. Lay this paper on the floor and lay some long straight guides along these lines. You might find that using string taped to the floor will make a good guide line. Mark the exact field of view angle and lay guides     Next, place your camera on the floor over the intersection of these guides, and shift it forward and backward until both guides are seen just along the vertical frame edges in the viewfinder. Switching to Live View may make this job easier. Be sure to stop down the lens aperture to get a deep depth of focus.   Also, you’ll want your camera to be level. I have a handy little bubble level that I keep in the camera’s hot shoe to check for level. Align the camera to split the angle Slide the camera to get the guides parallel to frame edges   Notice that the thin black guide lines are just along the frame edges in the shot above. Where the guides intersect under the camera/lens is the location of the correct pivot point (entrance pupil).   To verify the pivot point, go back to Method 1 using this location as a starting point to see if it's correct. You may need to fine-tune the location a little. 15-frame panorama after pivoting around the ‘entrance pupil’   I stitched the photographs together using Capture One  with ‘cylindrical projection’. This editor has several projection options. I like using Lightroom  for making panoramas, too. Nikkor AF-S 24-70 f/2.8 E ED VR at 24mm zoom setting     Shown above is another lens also zoomed to 24mm. Its entrance pupil is quite different than the 24-120mm lens. It should be obvious that the kind of severe offset of the camera and the center of gravity shown above requires a very sturdy tripod. The last thing you want is to have your tripod fall over with your camera and lens.     Entrance Pupil the Easy Way If he happens to include your lens, Bill Claff’s Photons to Photos database of lens information has already compiled the pivot information you need. Bill’s wonderful site has many lenses analyzed here, and you need to find the value of ‘P’  (entrance pupil) and ‘ I ’ (image plane) for your lens at the correct zoom setting. For the 24-70 lens shown above, his site link gives the values of P=34.76mm  and I=220.25mm at 24mm.  Just do the subtraction  I-P or  (220.25 – 34.76)= 185.5mm  to find the distance from the camera sensor to the tripod pivot location. At 50mm zoom, the pivot is at 181.25mm , and at 70mm zoom, the pivot is at 172.3mm .   These pivot numbers are pretty huge, requiring hardware with a long range of adjustment. This also requires strong tripod hardware.   I found out that Bill had also analyzed my 24-120 f/4S lens, unfortunately only after  I did the experiments mentioned above, and I got essentially the same results as Bill did. Bill got I@24mm = 130.96mm, P@24mm = 30.8 and I@120mm = 185.96mm and P@120mm = 126.43mm. This means the sensor-to-pivot at 24mm = 100.16mm. For the 120mm zoom setting, this means the sensor-to-pivot value is 59.5mm .   Bill has my 24-120mm lens listed as “Nikon 25-117mm f/4 IF”, which is why I didn’t find it at his site initially. He lists it according to the measured focal length versus the actual lens name.   Bill has lots of very nice information on his website, although much of the site is targeted more for scientist types.   Summary   Probably 99% of photographers would simply use the camera tripod socket location on their tripod for making panoramas. As demonstrated above, that would simply produce incorrect results. Don’t be that photographer; you’re better than that.    The procedures shown above could also be done with the camera in portrait orientation, but you better be sure that you have pretty heavy-duty hardware, a camera ‘L’ bracket, and a strong tripod.

I thought it would be interesting to show you how to find out (or verify) your lens’ focal length and its field of view.   One reason you might like to measure this stuff, versus just reading the lens focal length stamped on the lens, is that manufacturers often lie about the true lens focal length. This is particularly true of long zooms, which might not be as long as claimed. It’s often the case that a lens focal length reduces drastically when focusing close (called focus breathing), and these techniques could attach real numbers to that.   The diagrams above show the setup to align and measure your lens to get the information for calculating the focal length and field of view ( FOV ).   You only need to take 6 different measurements to calculate everything! The trick is in setting up the targets to make those measurements accurate.   The mathematics used in the calculations involves both algebra and trigonometry. Any “scientific” calculator has the necessary features to do this math. You can always download a scientific calculator app onto your smartphone. Fear not the math.   To get all of the necessary information, you’ll need to set up some targets on a wall (I used painter’s tape) and then take distance measurements at two different camera-to-wall distances. Carefully place tape at center and edges of the field of view   As shown above, I put some tape targets on the wall that point at the edges of the field of view and the exact center of the frame. I made sure that the distances on either side of the middle of the frame exactly matched. I also made sure that the lens was at exactly the same height as the middle wall target. Using high magnification via Live View or the viewfinder helps getting the targets more precise.   My setup was on a tile floor, and I used the tile grout lines to make sure the lens axis was exactly perpendicular to the wall. You could also temporarily tape a little mirror against the wall and line up the camera until you see your reflection in the center of the camera’s field of view. Laser for even better measurements   I happen to have a fun little laser that can make extremely accurate measurements over long distances. I used this device to get my targets placed within a millimeter, and to measure the camera-to-subject distance.   As I often say, “garbage in, garbage out”. The more accurate measurements you make, the more accurate your results will be.   I made all of the distance measurements relative to the lens axis and to a spot on the lens that I guessed to be near the vertex of the red arrows shown in the diagram. You don’t really need to know this location, since these techniques will actually calculate the location.   The nearer wall distance setup is called ‘ x ’. The farther wall distance setup is called ‘ X ’. Similarly, the distance along the wall from the frame middle to the frame edge in the nearer wall setup is called ‘ y ’, while the farther distance setup is called ‘ Y ’.   For both setups, the angular measurement from the lens axis to the frame edge is called ‘ Angle ’, measured in degrees. The FOV  of the lens is twice the value of ‘Angle’.   k  = Error Distance from lens measurement location to the true angle vertex.   k = ((y * X) – (x * Y)) / (Y – y)   x  = near_wall_distance from lens measurement location X  = far_wall_distance from lens measurement location   y  = (near_view_width) / 2 Y  = (far_view_width) / 2   Angle  = FOV / 2   Angle = ArcTangent (y/x)   x = y / Tangent(Angle)         and   X = Y/Tangent(Angle)   y = Tangent(Angle) * x         and   Y = Tangent(Angle) * X   FOV  = 2 * ArcTangent(y/x)  and FOV = 2 * ArcTangent(Y/X)   x_Actual  = x + k                   X_Actual  = X + k   Focal_length = (sensor_width * x_Actual) / (y * 2)       Example   I used my Nikkor 24-120mm f/4 S zoom at the 24mm position.   x = 1306mm y = 1085.85mm X = 2141mm Y = 1711.325mm   k = ((y * X) – (x * Y)) / (Y – y) k = ((1085.85 * 2141)-(1306 * 1711.325))/(1711.325 – 1085.85) k = 143.594mm   FOV  = 2 * ArcTangent(y/x)  FOV near = 2 * ArcTangent(1085.85/1306) = 79.48 degrees   FOV far = 2 * ArcTangent(1711.325/2141) = 77.27 degrees   x_Actual  = x + k x_Actual = 1306+143.594 = 1449.59mm   X_Actual = 2141+143.594 = 2284.59 mm   FOV_Actual = 2 * ArcTangent(1085.85/1449.59) = 73.67 degrees   Focal_length = (sensor_width * x_Actual) / (y * 2) Focal_length = (36 * 1449.59) / (1085.5 * 2) = 24.03mm   My angle vertex ‘guess’ at the front of the lens wasn’t very close. I had a calculated error of about 144mm.   It just so happens that the horizontal field of view of 73.7 degrees is what a 24mm lens has with a full-frame camera!   Summary   Using these techniques, you could actually find out what an un-marked lens’ focal length is. You could also verify (or debunk) manufacturer claims about the real focal length of a lens.

It’s in Nikon’s documentation that you can only use Pinpoint AF  while in the AF-S  focus mode. It turns out that even in this AF-S mode that you’re not allowed to select Pinpoint focus when you have assigned the “ Cycle AF-area mode ” to a button. I’m talking about assigning a button inside the Custom controls (shooting)  menu option.   I’m using the Nikon Z9 firmware version 5.0 the Z8 2.01 version. I just noticed this bug, but I assume it’s also a problem with older firmware.   If, instead, you go to the Photo Shooting Menu  and select Pinpoint AF inside the AF-area mode  there, you’ll be able to enable Pinpoint focus (assuming you are using Single-AF focus mode).   When I tried pressing the Sub-selector center button, it would cycle right past Pinpoint and invoke all of the other requested AF-area modes that are legal while in AF-S focus mode. 3D-tracking, for instance, isn’t allowed while in AF-S focus mode. Set Pinpoint AF here Custom controls (shooting) button assignment Assign Cycle AF-area mode Pinpoint AF gets ignored!! Pinpoint focus indicator   I hope that Nikon will eventually fix this bug.

I have known since the first day I got my Nikon Z9 that it focused better than any Nikon DSLR I have ever owned. When I got the Nikon Z8, I noted that it seems to focus exactly like the Z9.   I was a long-time holdout against mirrorless cameras, both because of their short battery life and their sluggish viewfinders. I didn’t see any particular advantage over DSLRs to persuade me to stop using my D850 or D500. Nikon eventually solved all of the mirrorless shortcomings that I knew about, and then some. I didn’t know just how much they had improved the focus system compared to DSLRs.   Instead of just ‘feeling’ like they focus more consistently, I did some tests to get some actual numbers comparing one of my mirrorless Nikons (the Z8) against my best DSLR: the Nikon D850. The camera sensors have the same resolution, so any measurements can be compared directly.   To eliminate any doubts about the lens being a limiting factor, I decided to use my 500mm f/5.6 PF Nikkor, which I consider my best lens, for the tests. Both cameras used the same ISO and exposure. I used a wired shutter release, and the D850 shots were done in “mirror-up” mode.  I manually de-focused the 500mm lens between each test shot, to force the cameras to do a full re-focus using AF-C.   My benchmark to evaluate focus accuracy is the lens resolution measurement, since higher resolution measurements correlate perfectly with accurate focus. I used a precision razor blade edge as my focus target, since it always gives me either equivalent or superior resolution measurements compared to my printed targets. I use the MTFMapper  program to evaluate my focus target photos.   I tested both cameras using phase-detect 3D focus. I’m not interested in comparing slow contrast-detect focus, even if it might be more accurate. My D850 has been autofocus fine-tuned with the 500mm lens; my Z cameras don’t seem to need this crutch, although they include that option in their menus.   I took many raw-format photos of a precision razor blade that is in silhouette. I don’t want to use any automatic sharpening (such as when shooting jpeg) to affect the resolution measurements. The camera/lens is on a heavy support, so that each shot has the blade silhouette in exactly the same location. Make sure that the razor blade is perfectly parallel to the camera sensor. Mirrorless Z8 versus DSLR D850 The focus subject is a slanted high-precision edge   The shot above shows the MTFMapper  dialog used to perform “manual edge selection”. I have a razor blade with strong back-lighting as a target, and I put the camera focus point over the center of the razor’s sharpened edge. After using the computer mouse to select the portion of the blade image to use, I let the MTFMapper  evaluate this edge to determine the lens resolution at this position and orientation.   The MTFMapper  program lets me select all of the test photos at once; it assumes the target in each shot is at exactly the same position. I make sure that “ reuse ROIs ” is selected, and then click the “ Accept Queued ” button to have the program evaluate all of the photos without further intervention by me. A typical shot after MTFMapper  has finished evaluation   You can see a little cyan-colored MTF50 resolution measurement superimposed over the location on the blade where I requested the program to evaluate the resolution. In this shot, the MTF50 resolution measurement is 84.8 lp/mm.   I put all of the measurement results from MTFMapper  into an Excel  spreadsheet. I then plotted the resolution measurements against the camera filename (frame number). D850 resolution variation with 500mm f/5.6 PF, AF_tune -4   The plot above shows the variation in resolution measurements for the Nikon D850. Again, I de-focused the 500mm lens and then refocused between each shot, to force the camera to perform a new phase-detect, AF-C focus in 3D-tracking mode.   The D850 results got an average MTF50 resolution of 63.2 lp/mm , with a peak reading of 81 lp/mm  and the standard deviation (spread of measurements) was 8.12 .   Since there was a single measurement higher than the others, the autofocus fine-tune setting could possibly be re-adjusted to get overall better focus, although the photo EXIF data in every frame indicates the same 4.47m focus distance. The spread  of the measurements isn’t affected by the autofocus fine-tune setting.   Bear in mind that resolutions above 40 lp/mm will all appear pretty sharp, so these results are still good. Nonetheless, I decided to change the AF-tune and re-try the shots. D850 resolution variation with 500mm f/5.6 PF, AF_tune -2   The D850 with the new AF-tune -2 results got an average MTF50 resolution of 71.7 lp/mm , with a peak reading of 84.8 lp/mm  and the standard deviation (spread of measurements) was 10.3 .   The slight AF-tune adjustment change definitely helped! Notice that there is sort of a split in the data. When I was shooting the target, I would de-focus the lens by alternating too near and then too far shot-to-shot. The camera seems to have a bias in focusing based upon the direction to achieve focus.   I don’t know if something might have shifted or drifted over time with the focus calibration. It was definitely worth re-checking this, since it resulted in a typical gain of about 13 percent resolution. Z8 resolution variation using 500mm f/5.6 PF   The plot above shows the variation in resolution measurements for the Nikon Z8. Again, I de-focused the 500mm lens and then refocused between each shot, to force the camera to perform a new phase-detect, AF-C focus in 3D mode.   The Z8 results got an average MTF50 resolution of 74.0 lp/mm , with a peak reading of 98.2 lp/mm  and the standard deviation (spread of measurements) was 6.7 .  With the exception of the single reading of 98.2, the data was much more tightly grouped than the D850 results. I think that the 98.2 reading is some kind of a fluke which should probably be ignored.   If you’re interested, the average resolution of 74 lp/mm is equivalent to 3537 lines per picture height. I prefer using ‘lp/mm’ units, since it applies to any size sensor.   I didn’t notice any bias in resolution related to focusing from near-to-far versus far-to-near, either. The Z8 (and Z9) are just smarter about focus.     Summary   The Nikon Z8 (along with its big brother the Z9) has noticeably better focus consistency than the D850. After seeing how the D850 results dramatically improved with such a small AF-tune adjustment, I should probably explore using that option on my Z cameras, too.   Before testing with my Z8/Z9 cameras, I would have said that my Nikkor 500mm f/5.6 PF lens had a typical center resolution of about 63  lp/mm when using 3D continuous autofocus on my D850. After studying those results and modifying the autofocus fine-tune, I changed my mind to conclude that the resolution was closer to 71  lp/mm. Now, I can say that it has a typical center resolution of roughly 74  lp/mm when using 3D continuous autofocus on the Z8/Z9 cameras.   If you only shoot using slow contrast-detect focus (via Live View on the D850) then these focus (resolution) differences will largely disappear. If your lens has focus-shift issues when changing the aperture, then the focus variation differences between DSLRs and mirrorless cameras will increase . The Nikon mirrorless cameras focus at the shooting aperture when using phase-detect (through f/5.6), but the DSLRs don’t.   You need to shoot many tests and study those results to guide yourself toward optimal calibration, in the case of DSLRs. Statistics exist for a reason; you can’t really know how your gear performs without doing lots of testing. It’s possible that your mirrorless Nikon could squeeze a bit more sharpness out of a lens with autofocus fine-tuning, as well.   Mirrorless definitely wins the war of consistency over DSLRs when using phase-detect focus.