Many of you are aware that you can use the beloved 35mm f/1.8 DX lens with an FX sensor. I have an on-going love affair with this lens, but if anybody mentions it to my wife, I’ll flat-out deny it. There are many discussions about the ‘vignetting’ levels when you try this lens on FX, but there is precious little data on the “corner sharpness” when you decide to misuse/abuse this lens by mounting it on an FX body. Not to mention how the focusing distance affects vignetting. This article explores the practicality of using the 35mm f/1.8 DX lens with an FX sensor. The news is good. You don’t need to abandon what (to many) is their absolute favorite DX lens that Nikon produces. The coverage (the image circle) of the 35mm f/1.8 DX shows how this lens is an over-achiever. It goes above and beyond what is required for a DX sensor; it’s almost as if Nikon designed this lens for FX, but accidentally labeled it as “DX” instead. Almost. To be honest, the corners do get a bit dark, especially when the lens is focused near infinity. The secret sauce is to use the “vignette control” in image-editing software to lighten corners, and to not stop down the lens too much. The post-processing solution isn’t perfect, but for many photographs, it will make it turn vignetting into a “don’t care” situation. Believe it or not, the corner resolution isn’t that bad, either. It’s not as good as an “FX” lens, but most people won’t even notice the difference between this “DX” lens and an “FX” equivalent. At a fraction of the cost and a fraction of the size and a fraction of the weight. The bottom line, assuming that you want to be able to focus at infinity, is to keep your lens between f/1.8 and f/4.0. This isn’t much of a hardship. If you want to stop down further, then yes, you’ll need to crop a bit, but only just a bit. 35mm f/1.8 AF-S DX mounted on an FX Nikon D610 Since talk is cheap, let’s look at the data. Nikkor 35mm AF-S DX at f/1.8, with no distortion correction, using Nikon D610. You can barely make out any vignetting in the resolution chart (4.6 feet away). The vignetting was corrected using Capture NX2, but the correction is almost identical using other tools, like Photoshop. You can tell there’s some barrel distortion, though, so let’s try to fix that next. Nikkor 35mm AF-S DX at f/1.8, barrel distortion removed, Nikon D610. Now, there’s no visible distortion and any vignetting is almost gone. For normal photography, you’d not notice any vignetting. Nikkor 35mm AF-S DX at f/4.0, vignetting/barrel distortion removed, Nikon D610. Note that vignetting is still almost imperceptible at f/4.0, and I’ll bet nobody would be complaining about edge sharpness, either. You can even get away with f/5.6 and not have vignetting trouble, unless you try to focus at a long distance. I'd say that the vignetting here is about the same as the Nikkor 18-140mm AF-S DX lens on a DX camera. Nikkor 35mm AF-S DX at f/1.8, focus near infinity, Nikon D610. No free lunch. Now, it’s time to look at some warts. The picture above was focused near infinity, and the lens had both a hood and a UV filter on it. Cropping is becoming a necessity under these conditions, but the angle of view after cropping still far exceeds the Nikon in-camera “automatic DX cropping” that the camera offers. Using a UV filter and a hood don’t make a perceptible difference with vignetting; the lens image circle is the limiting factor. Resolution So, how does the resolution at the FX frame edges stack up? The following charts tell all. MTF50 lp/mm at f/1.8. The center, of course is already terrific. Corners aren’t. MTF50 lp/mm at f/2.8. The center is very, very good. Corners still aren’t. MTF50 lp/mm at f/4.0. The center is stellar. Corners are now acceptable. Conclusion With only a few concessions, this lens is quite useable on FX. Speaking for myself, it’s a keeper for either DX or FX. #review

This is a basic test to perform before the return date expires on your new lens. Keep this test in mind if you ever accidentally give your lens a hard bump, too. This idea comes from Roger Cicala at this link: It’s cheap and easy to perform. The trick is to get your photos properly out-of-focus. I never thought I would give anybody that kind of advice. Also, you’ll want to under-expose your shot, since camera meters aren’t very smart about subjects like this. Use notebook paper reinforcing rings stuck onto black construction paper. What you want is to get an idea of how the corners differ from the center and from each other. I fortunately don’t have any lenses with gross de-centering, so my shots show nice symmetric fuzzy circles. According to Roger, there are very few lenses (some super-wides and mega-zooms) that might give a false-positive bad result. It’s not important if your shots are out of focus in front of or behind the rings. What you do want is for the middle of the rings to still show just a little black. The following shots demonstrate an 85mm lens and a 600mm lens test. 85mm lens f/1.4 Len Centering Chart properly out-of-focus 600mm f/6.3 All circles are boringly perfectly circular. Look for circle characteristics that aren’t symmetrical; depending upon your lens, it’s expected that the corners won’t look exactly like the center, but each corner should demonstrate similar characteristics to the other corners. Chart too out of focus. Centers have gone from black to white. I prefer to shoot lenses wide-open for these tests, which will tend to magnify any lens faults. There you have it. An easy, inexpensive lens-screening test. Remember this test when you buy your next lens to give it a quick once-over. May your circles be symmetric. #howto

It might seem shocking at first to see that your full-frame camera can have poorer lens resolution scores than the cheapo APS-C sensor. Here’s what is probably going on. Your small-frame sensor probably has smaller pixels than that full-frame camera does. Smaller pixels means more pixels per millimeter on the sensor, and hence more lines per millimeter, too. Here’s a specific example. Let’s compare the D7100 to the D610. Both cameras are roughly 24MP, so you’d think that they would score about the same. D7100 4000 X 6000 pixels, and has dimensions of 3.92 microns for each pixel. The D7100 sensor itself is 15.6 mm X 23.6 mm. D610 4016 X 6016 pixels, with 5.95 micron pixels and is 24.0 mm X 35.9mm. Let’s look at some resolution measurements, using the same lens at the same f/stop. Here, I’m using the Sigma 150-600 at 600mm, f/6.3. D7100 with Sigma 150-600 at 600mm f/6.3 tops out at MTF50 of 40 lp/mm D610 with Sigma 150-600 at 600mm f/6.3 tops out at MTF50 of 34 lp/mm Did I get ripped off?? Why is the resolution so much worse with the D610 compared to the D7100? The secret lies in the pixels. There are less pixels per millimeter in the D610, and therefore less MTF50 lp/mm resolution. But there are more millimeters in the D610 sensor! The key measurement of interest here is in line pairs per picture height (lp/ph). The math: lp/ph = lp/mm * mm_of_height The D7100 sensor height is 15.6 mm. The D610 sensor height is 24.0 mm. For the above measurements, the D7100 measures 40 lp/mm * 15.6 mm = 624 lp/ph The D610 measures 34 lp/mm * 24.0 = 816 lp/ph. So, the D610 wins after all. It has a ‘score’ of 816 and the D7100 has a ‘score’ of 624. More total lines of resolution in the photo for the D610. But wait, there's more: D610 pixel area = 35.4 square microns D7100 pixel area = 15.4 square microns This means that the D610 pixels can drink up more than twice the light per pixel, which makes for vastly superior low-light and high-ISO abilities. You can also achieve narrower depth of focus with the full-frame sensor, so you have more options photographically. Feel better now? #howto

This is a pre-AI model, and was tested on the D5000, which Nikon specifically states is incompatible with this camera. Hmm. This lens was the reason many people bought Nikon. In its day, it was the portrait lens to get. I remember Linda McCartney using this lens to take pictures of Paul in a televised concert. It’s my understanding that she could afford to use whatever gear she wanted, seeing as her husband was already a near-billionaire at the time. This lens version had anti-reflection coating (the "C" in the lens designation). This is another lens that was used in the making of the original Star Wars movies. The MTF50 measurements presented below, being produced from a 12MP camera, don’t look as high as more modern high-resolution sensors. This lens won’t fit my other cameras, and isn’t one that can be updated to “AI”, either. Focus Silky smooth, but totally manual. When you could get cameras with split-prism focusing screens, focus was a breeze. With cameras these days, manual focusing is a lot tougher. Such is progress. I had thought the D5000 “rangefinder focus” would be the answer, but it won’t work for these manual lenses. Oh well. Nikkor-P C 105mm f/2.5 with HS-4 hood on D5000. An elegant lens. Resolution Testing These tests were done using a Nikon D5000 (12 MP) with unsharpened RAW format. Resolution is a 2-dimensional thing. The tests that follow show you how resolution varies throughout the frame. Also, the sagittal direction is really, really good. The meridional direction isn’t as good, but is still better than most lenses. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in my MTF Mapper Cliff’s Notes article. The software is comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. I can’t thank the author of MTF Mapper, Frans van den Bergh, enough. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. If you spot some small islands of resolution peaks/dips in the following charts, you can safely ignore them. Visually imperceptible variations in the surface of the resolution chart can show up rather dramatically in the plots, because the analysis software is exquisitely sensitive. What the resolution target looks like. Mine is mounted ‘upside down’. Finally, I’m getting around to some actual resolution results. Tests were done with “Live View” manual focus at maximum magnification and IR remote. I use the “best of 10 shots”; not every shot gets the same resolution results. Corner, wide open at f/2.5 target squares cycles/pixel. Sagittal beats meridional. Center, wide open at f/2.5 target squares cycles/pixel. The corners aren’t really good until f/4.0, but the center is terrific at all apertures until a little beyond f/16. You don’t want to use f/16 or beyond if resolution is important to you. Diffraction kills sharpness. I didn’t bother to measure, although this lens lets you set the aperture all the way down to f/32. The resolution of this lens leaves almost nothing to complain about. The corners, which are a “don’t care” nearly all of the time for most people, need f/4.0 or more. Conclusions If you’re a “manual” kind of person who likes to be in charge of what is going on, then this just might be the “it” lens for you. Bear in mind that the lens mount doesn’t permit being mounted on the latest Nikons, and this version cannot be “AI converted”. I have always enjoyed using this lens for portraits, and it gives you enough working room that your subject is invariably more at ease. You can’t exactly quantify it, but this lens just feels right. Sample Picture Crop from a head shot. The eyes tell the story of this lens. #review

This is the lens produced from 1969-1979. It’s a hard-core pre-AI model, and was tested on the D5000, which Nikon specifically states is incompatible with this camera. Guess they never tried it. Did you know that this was the lens used to film the battle cruiser in the opening scene of the original Star Wars movie? George Lucas was after the maximum quality he could get, and he got it. They moved the lens over the model of the ship on a motor-driven slide, instead of moving the ship past the lens. It was filmed by Richard Edlund, who also created the opening scene for Star Trek, where the starship Enterprise whizzes past, and he worked on Raiders of the Lost Ark as well. Richard got several Oscars in his career, and was always a big fan of Nikon. Nikon built this lens with supreme mechanical precision; it works as well today as it did when it was brand new. The MTF50 measurements presented below, being produced from a 12MP camera, don’t look as high as more modern high-resolution sensors. The problem is, though, that the lens won’t fit on those cameras. Focus As smooth as smooth can be, but totally manual. I actually dropped this lens onto a granite boulder when I was on a hike in the 80’s, but it still works perfectly. A moment etched into my memory. Not many lenses would have survived that treatment. A word about the D5000 here. They have an “electronic range finder focus" manual focus scale in addition to the “idiot dot” focus confirmation. Ironically, the premium range finder focus scale is unavailable while using this manual-focus lens, and all you get is the idiot dot. How’s that for a camera design? The lens focuses from infinity to half-life-size, but it can focus down to life-size if you use the PK-3 ring that it comes with. This is probably the most premium focus scale ever produced on a non-cinema lens, since precision and accuracy were what this lens design was all about. 55mm f/3.5 Micro-Nikkor on D5000 55mm Micro-Nikkor in full regalia on PB-4 bellows Check out this shot. That’s the PB-4 bellows with the lens reverse-mounted for maximum sharpness when going beyond life-size. I got this equipment back in the day when figuring out exposure for slides would put hair on your chest. This shows the following: BR-2 ring to mount the lens in reverse, using the 52mm filter threads. The lens is sharper reverse-mounted when using magnifications beyond life-size. BR-3 ring mounted on the rear of the lens to permit keeping a 52mm filter over the lens, in addition to protecting the rear portion of the lens and acting as a lens hood. BR-4 ring to keep the lens opened at maximum aperture until you take the shot. AR-4 release (one cable fits into the BR-4, the other cable threads onto the camera shutter release (e.g. Nikon F2 shutter) to coordinate stopping the lens down prior to tripping the shutter. PB-4 bellows, which features tilt-shift controls and of course holds the slide-copy and film strip attachment up front. It also has click-stops to hold the camera either horizontal or vertical. (Slide copy attachment not shown). I have separate attachments to mount flashes up front on the bellows, but it’s typically easier to just use a card and bounce flash from the camera-mounted flash. Resolution Testing These tests were done using a Nikon D5000 (12 MP) with unsharpened RAW format. Resolution is a 2-dimensional thing. The tests that follow show you how resolution varies throughout the frame. Also, the sagittal direction is really, really good. The meridional direction isn’t as good, but is still better than most lenses. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in my MTF Mapper Cliff’s Notes article. The software is comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. I can’t thank the author of MTF Mapper, Frans van den Bergh, enough. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. If you spot some small islands of resolution peaks/dips in the following charts, you can safely ignore them. Visually imperceptible variations in the surface of the resolution chart can show up rather dramatically in the plots, because the analysis software is exquisitely sensitive. What the resolution target looks like. Mine is mounted ‘upside down’. Finally, I’m getting around to some actual resolution results. Tests were done with “Live View” manual focus at maximum magnification and IR remote. I use the “best of 10 shots”; not every shot gets the same resolution results. The corners aren’t good until f/5.6, but the center is terrific at all apertures until a little beyond f/16. You don’t want to use f/16 or beyond if resolution is important to you. Diffraction kills sharpness. I didn’t bother to measure, although this lens lets you set the aperture all the way down to f/32. The resolution of this lens is wonderful. It’s easy to see why it was Big Man On Campus during its time. It’s amazing how well this lens measures up today, considering the limited tools and materials available to lens designers in the 60’s and 70’s. Conclusions If you don’t mind slowing down your pace a bit, this lens can produce images second to none. It’s a shame that the lens mount doesn’t permit being mounted on the latest Nikons. Back in the day, Nikon engineers seemed to be more fanatical about close-up photography. I bet most of you have never even seen the PB-4 bellows and its really cool attachments. The next time you watch the first Star Wars movie, think about the lenses that shot it. Sample Pictures Protea flower, high magnification, 55mm reverse-mounted on PB-4 Whole protea flower, f/8 #review

This review will emphasize the lens MTF50 resolution performance and how well the lens auto-focuses. I was feeling guilty about not writing a review of what is probably the most populous Nikon lens of the modern age. So here it is. The lens is so light that it feels like it’s filled with helium. It’s supplied with a lens cap and an end cap and … nothing. The lens has a plastic lens mount and no rubber seal. Exactly as you’d expect. So what DOES this lens have? It has resolution. And it’s my go-to lens for infrared. Large, quality infrared filters are devilishly expensive, so the 52mm filter threads on this lens are a welcome sight. Focus This lens won’t let you override auto-focus with the focus ring, which I used to think was a ‘given’ with AF-S. Wrong. You have to switch the lens to “manual” focus. Major complaint here. The auto-focus fine-tune on this lens is ZERO at 55mm, but it’s -4 at 18mm (these numbers are for my D7100, but different on the D7000). Since this isn’t a Sigma lens with the ability to fine-tune at various focal lengths and distances, I’m kind of stuck unless I stop the lens down to f/8 or so. I decided to split the difference and set the fine-tune on -2. The skinny plastic focus ring is right behind the 52mm filter. There is no focus scale. Given this meager working set, it can be tricky to manage getting the lens focused, keep the focus ring steady, and screw on an infrared filter. The auto-focus DOESN’T have any chatter using my usual AF-C and rear focus button. Yay! Speaking of auto-focus, this lens is more in the ‘turtle’ category than the ‘rabbit’ category. At least it eventually gets there. I exaggerate, of course. Nikkor 18-55mm on the D7000. Using my classic (1974!) L39 filter. Get a load of that world-record-skinny focus ring knurling behind the filter! Speaking of the filter, it’s not one you’d want to point toward the sun. It’s uncoated, but it has been my friend most of my life and I could never get rid of it. Vibration Reduction (VR) This version of the lens has VR; the original version didn’t. Newer versions now have “VRII”. I was able to get about 2.5 stops of anti-shake, but my results vary a lot. Everybody is different in how they support the camera while hand-holding it, so any quote about VR effectiveness isn’t really a rule; it’s more of a guideline. Yes, that line was stolen from Jack Sparrow. Resolution Testing This review is looking at a single copy of the lens. Yours will be different, but hopefully ‘similar’. Some day I might get around to testing more of these things, since I have a few more laying around. These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. Resolution is a 2-dimensional thing. The tests that follow show you how resolution varies throughout the frame. The resolution charts are split into “sagittal” direction (like wheel spokes) and “meridional” directions. These directions match the MTF references published by Nikon. What’s different, though, is the following values were MEASURED versus Nikon’s “theoretical” values. Also, the sagittal direction is quite good. The meridional direction isn’t nearly as good and is the culprit in dragging down the MTF50 numbers. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also includes files for printing out the resolution targets (mine are A0 size on heavy glossy paper, dry-mounted onto a board). This program is covered in more detail in my MTF Mapper Cliff’s Notes article. The software is comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, provides this excellent software for FREE. Visit his site and give him the praise he so richly deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, except in the most expensive of optics. If you spot some small islands of resolution peaks/dips in the following charts, you can safely ignore them. Visually imperceptible variations in the surface of the resolution chart can show up rather dramatically in the plots, because the analysis software is exquisitely sensitive. What the resolution target looks like. Mine is mounted ‘upside down’. At long last, I’m getting around to some actual resolution results. Tests were done with “Live View” AF-S auto-focus, contrast detect, IR remote (via a cell phone), VR OFF, and a really big tripod. I use the “best of 10 shots”; not every shot gets the same resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce. Corner at 18mm f/3.5 Center at 18mm f/3.5 Conclusions While definitely not a ‘pro’ lens, this lens is still capable of producing some fine photographs, even wide open. You can’t beat the price. Without a distance scale, even manual focus can be a challenge. With my copy, the longer focal lengths are the weakest (typical of almost all zooms, by the way). Corners aren’t stellar, but surprisingly good. The center is really good at all focal lengths; nothing to complain about here. My own style dictates that I use this lens at 18mm maybe 90% of the time. Luckily, it has great optical performance at that length. Sample Pictures 18mm f/10 Hoya R72 (Infrared) with Red/Blue color channel swap Sequoia 18mm HDR using Efex Pro2 HDR. Some chromatic aberrations visible #review

This review mostly details the lens MTF50 resolution performance and how well the lens auto-focuses. I don’t need to rehash the Nikon specifications of the lens. Is it just me, or does that lens title seem like all it’s missing is “EIEIO”? You can pick up this lens for dirt cheap, so bear that in mind if you notice any whining in the subsequent paragraphs about things that only exist on pricier lenses. The lens feels like it weighs nothing, and it’s really short for being able to zoom to 200mm. It has a good solid (plastic) bayonet lens shade that will reverse-mount on the lens for really compact storage. It telescopes out as you zoom to 200mm. The lens has a plastic lens mount and no rubber seal. What a shocker ;~) Focus This and the 18-55 kit lens are the only AF-S Nikkors I’m aware of that you can’t override auto-focus with the focus ring. You have to switch the lens to “manual” focus. Yuck. The skinny plastic focus ring is right behind the 52mm filter. Double yuck. If you can stick to auto-focus, though, it’s no problemo. There is no focus scale. Did I say yuck yet? The auto-focus DOESN’T have any chatter. Yay! Beats that evil 70-300 zoom. Speaking of auto-focus, this lens is unfortunately the poorest example I’ve seen from Nikon. It’s slow, and even refused to operate in “cloudy bright” conditions when I tried Live View at f/8.0 on the D7100. The 18-55 kit lens focuses much better. Stick to phase-detect focus. At least it didn’t have any focus chatter. Or did I already mention that? Nikkor 55-200mm zoomed out to 200mm with HB-37 hood Zooming out and using the hood makes it look like a much larger lens. When zoomed to 55mm and having the hood reverse-mounted, it stores away in a really small space. Vibration Reduction (VR) This version of the lens has VR; the original version didn’t. I was able (sticking to decaf) to get about half of my shots sharp at 1/100s with NO VR while zoomed to 200mm. Using VR, I could go to roughly 1/50s. I even got one sharp shot (out of 5) at 1/13s with VR ON. If the rule of thumb is 1/(35mm focal length equivalent) limit, or 1/300s then you could say the VR is good for about 2.5 stops. Everybody is different in how they support the camera while hand-holding it, so your mileage will vary here. I determine “sharp” versus “un-sharp” by photographing a resolution chart at slow shutter speeds and measure where the resolution (MTF50 lp/mm) drops by about 10% from maximum. I don’t know if there is some industry standard on VR effectiveness, but what counts for me is when pictures just start to show some blur, and I like to do it by the numbers. I haven’t figured out how to calibrate my level of nervousness with hand-holding, so this VR business is literally “hand waving”. Oh, also, I test at the longest focal length (200mm). Resolution Testing This review is looking at a single copy of the lens. Yours will be different, but hopefully ‘similar’. These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. Resolution is a 2-dimensional thing. The tests that follow show you how resolution varies throughout the frame. If you ignore the corners, then resolution is really quite good. About time I said something positive about this lens, isn’t it? Also, the sagittal direction is really, really good. The meridional direction, on the other hand, is really quite terrible and is the culprit in dragging down the MTF50 numbers. I have a few shots below that demonstrate what I’m talking about. You’d swear there was severe motion blur in the pictures, but it’s just the meridional direction optical aberrations. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in my MTF Mapper Cliff’s Notes article. The software is comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. I can’t thank the author of MTF Mapper, Frans van den Bergh, enough. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. If you spot some small islands of resolution peaks/dips in the following charts, you can safely ignore them. Visually imperceptible variations in the surface of the resolution chart can show up rather dramatically in the plots, because the analysis software is exquisitely sensitive. What the resolution target looks like. Mine is mounted ‘upside down’. At long last, I’m getting around to some actual resolution results. Tests were done with “Live View” AF-S auto-focus (where possible), contrast detect, IR remote, VR OFF, and a really big tripod. For f/8 and beyond, I was forced to use manual focus using Live View at 100%, since it refused to focus automatically. I use the “best of 10 shots”; not every shot gets the same resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce. 55mm f/4.0 APS-C Corner. Note Sagittal is MUCH better than Meridional The corner at 55mm f/4.0 shows how much worse the meridional direction is than the sagittal direction. Also note the vignetting (I don’t care much about vignetting, since it’s easy to fix in post processing). There is very slight chromatic aberration (this is the unmanipulated RAW view), which is also trivial to fix in post. 55mm f/4.0 center looks good 200mm f/5.6 corner. Good unless you count the meridional direction! Lens center 200mm f/5.6. Unusually poor dead center, but much better resolution just a little off of center. See 2D plots below for overall resolution view. Conclusions While not in the ‘pro’ category, this lens is still capable of producing some fine photographs, even wide open. If you can tolerate f/11, it’s capable of truly good shots. It’s all about knowing a lens strengths and weaknesses. For 200mm, it’s exceptionally portable and light. You can’t beat the price. I’d avoid low light levels; without a distance scale, even manual focus can be a challenge. The picture below gives you a hint of what the lens is capable of doing with a bit of practice. Sample Picture Rabbit at a dead run, 1/500s f/5.6 55-200mm at 200mm, ISO 400, VR ON, 37 feet. Very few shots require sharp corners. This shot has always been a favorite of mine, done with one of the cheapest and least glamorous lenses that Nikon makes. It looks quite sharp, even in a print I have that’s 36 inches wide. It was taken by my daughter, who got her amazingly fast reflexes by competing in fencing (foils) competitions for years. Try shooting wild rabbits on the run and you’ll appreciate the shot even more. #review

Most consumer cameras don’t offer focus calibration (auto-focus fine-tune). Many users of enthusiast/professional cameras ignore focus calibration as “a waste of time”. After all, the factory makes nearly every lens and camera fully calibrated, right? Fully not. Top ten things that can use tuning: Cars Musical instruments Husbands/boyfriends Skis Lasers Voices Radio stations Software algorithms Computers Cameras/Lenses Notice that cameras and lenses just made the list. I have never shot with a camera/lens combination that needed a focus calibration of “zero”. Maybe they exist somewhere. Even the 85mm f/1.4 AF-S Nikkors (I’ve tested two of them) need focus calibration at some of their wider f-stops. What kind of price do you pay by not calibrating? Can you even tell the difference? This article shows you what kind of price you pay. My lenses use focus calibration values that range from as little as “+1” to as much as “-20”. The full range of calibration values among all of my lenses varies from “-20” to “+15”. Since the Nikon range is +/- 20, I’m right on the hairy edge. So what happens if you don’t bother to calibrate? You pay a big price in resolution, that’s what. If you only own really slow lenses or only shoot with the lens stopped down quite a bit, then it might be a truly “don’t care” situation. The higher-resolution camera sensors are even more picky about focus calibration. I did a set of tests with my Nikkor 35mm f/1.8 AF-S (DX) on a D7100. It falls into the category of “average” focus calibration, needing a value of “+7”. Not too much fine-tuning compared to my 60mm Micro-Nikkor that needs “-20”, but still nothing to sneeze at. My D7000 needs a fine-tune adjustment of “-5” with the same 35mm lens on it. The following are my test results, conducted with the MTF Mapper program and using an A0 size resolution chart. I turned on phase-detect auto-focus and then switched auto-focus fine-tuning OFF for half of the tests. I tested shooting wide-open, and then I tried stopping the lens down a bit more than 2 stops and re-tested. I forced the lens to minimum focus distance, then used the “AF-ON” button assignment to re-focus between every shot. Take a look at my MTF Mapper Cliff's Notes article on how to perform focus calibration using a proper focus chart and software that can provide definitive answers about if you're in focus or not. First Test: Focus Fine-Tune is OFF f/1.8 Lens Center MTF50 lp/mm Measurements 32 34 32 36 34 f/4.0 Lens Center MTF50 lp/mm Measurements 65 70 70 70 70 Second Test: Focus Fine-Tune is ON (+7) f/1.8 Lens Center MTF50 lp/mm Measurements 50 50 50 50 50 f/4.0 Lens Center MTF50 lp/mm Measurements 70 70 70 70 70 The average f/1.8 MTF50 lens center resolution with no focus fine-tune was 33.6 lp/mm. The average f/1.8 MTF50 lens center resolution with focus fine-tune ON was 50 lp/mm. The average f/4.0 MTF50 lens center resolution with no focus fine-tune was 69 lp/mm. The average f/4.0 MTF50 lens center resolution with focus fine-tune ON was 70 lp/mm. At maximum aperture, the resolution change using fine-tune calibration was HUGE (it went from 33.6 to 50). With the lens stopped down, the resolution change was minimal. So there you have it. If you camera doesn’t have focus fine-tune, then get one if you can afford it. Or else buy Sigma lenses that support their USB calibration dock for in-lens calibration. If you only shoot lenses stopped down, then you can probably safely ignore focus calibration. #howto

This article will concentrate on the Nikkor 50mm f/1.8 AF-D MTF50 resolution performance and discuss how well the lens autofocuses. Repetition of the published Nikon specifications of the lens will be mostly avoided. This is one of the most popular Nikkor FX “prime” lenses ever produced, known as the “nifty fifty” (the 50mm f/1.4 shares this title, but the price of the 1.8 makes it much niftier). It’s also one of the most inexpensive Nikkor lenses. I’ve paid more for filters than I did for this lens. This is another of the Nikkor lenses that falls into the category of “just get one”. It’s reasonably fast, focuses well, and is one of the tiniest lenses Nikon has made. It has been superseded by the “G” version, which loses the aperture ring. When used on DX cameras, this is a particularly good focal length for portraits (75mm equivalent). What you don’t get: vibration reduction and great corner resolution when the aperture is wide open. My usual disclaimer: this is looking at a single copy of the lens. Yours will be different, but hopefully ‘similar’. The only place I know of that tests lots of copies of lenses is here. I was lent another copy of this lens (not being reviewed here) and it was NOT good. You need to verify your own copy; I don’t believe that Nikon tests each lens, or else the other copy I was lent wouldn’t ever have made it out of the factory. These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. Given this fact, I’m not reporting on the edge performance of an FX sensor. Here is a link to get pretty good information on this lens. My main complaint with them (and most of the other web sites) is that they simplify resolution measurement down to a single number for an f/stop. It’s not that simple; resolution is a 2-dimensional thing (not to mention sagittal/meridional directions within those 2 dimensions). The focus ring on this lens is a wide-enough one, nearest the filter. Being a “D” lens, you can’t just use it anytime you want to override autofocus; you need to set your camera into manual focus mode first. Note: keep your hands off the lens during auto-focus; the focus ring will spin around! I’m guilty of virtually never overriding auto-focus on a short lens like this, so manual focus considerations are a “don’t care” for me on this lens unless I’m shooting infrared. The lens also has a proper metal lens mount, but no gasket (rubber seal). There’s no dust/weather resistance. There is a distance scale. Comes in very handy for infrared when I can’t see the subject through the viewfinder. Also note: DO use this lens for infrared! I use it with the Hoya R72 52mm IR filter. There is no “hot spot” in infrared that often happens with lenses, so it works fine for that purpose (in manual focus mode, of course). Nikkor 50mm f/1.8 AF-D FX with 52mm filter. Tiny lens! Autofocus Only works on cameras with the built-in “screw drive” focus motor. If your camera doesn’t have the screw drive, then you will need the more expensive “G” version of the 50mm. All of my lenses need some focus fine-tune calibration; so does this lens. The focus speed is largely controlled by which camera is attached. I haven’t seen repeatability issues on either my D7000 or D7100, and the focus speed has been more than enough. Vibration Reduction (VR) Nope. Helps keep this lens inexpensive. Even Nikon’s 85mm f/1.4 AF-S doesn’t have VR. Just saying. I wish all my lenses had VR, but such is life. MTF50 Resolution Testing This is why you should read this article. I will provide the information to enable you to evaluate resolution between lenses in a standard, scientific way yourself, if you wish to double-check me. Also, since your lens results will be different than mine, the following results are just a guideline. See my MTF Cliff’s Notes article to be able to repeat these tests for yourself. Resolution measurements are in MTF50 lp/mm. This measurement represents how many image line pairs can fit inside a millimeter before the white-to-black chart transitions degrade to 50%; e.g. “turn to mush”. For me, anything beyond about 30 lp/mm is fine, and beyond 50 is outstanding. Higher-resolution sensors yield higher measurements, much like you’d expect. Before I forget, you will notice a couple of weird blobs in some of the resolution plots that follow. Please ignore these, since they are definitely not a lens imperfection. The measurement software is extremely sensitive, and an imperceptible chart surface indentation shows up very clearly in the measurements. The real resolution reference is the annotated photograph of the resolution chart, which shows each little square’s edge in “cycles per pixel” units. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in another article, but suffice it to say that this is really great stuff; it’s comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, really knows his stuff. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. The meridional/sagittal differences are what “astigmatism” is all about. This lens is decent in the sagittal direction when you get away from the lens optical center, and corners are “okay”. Meridional direction isn’t as good, but judge for yourself in the ensuing resolution plots. The middle of the lens is impressive, as you’ll see. What the resolution target looks like. My target is mounted ‘upside down’. At long last, I’m getting around to some actual resolution results. Tests were done with “Live View” AF-S autofocus, contrast detect, IR remote (cell phone, actually), and a really big tripod. That’s how I get around any phase-detect problems with focus calibration. The results don’t seem to improve using manual focus and 100% magnification in Live View, so I don’t bother. I use the “best of 10 shots”; not every shot gets the same resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce. Frans van den Bergh has an article on how he tested the Nikon D7000 phase-detect focus accuracy by doing a series of tests starting at minimum focus and then a series of tests starting with the lens focused at infinity. He found a definite correlation showing how the camera stopped focusing once it decided that focus was “good enough”, so the infinity-focus-start series would focus a little behind the target, and the start-at-minimum-focus-distance series would end up with focus a little in front of the target. Acceptable center wide open, but corners are a bit off (f/2.0 is similar). Already good edge-to-edge at f/2.8 Stellar center performance by f/4 Peak performance at f/8 Diffraction is exacting its toll at f/16, but still quite good Sample Pictures Fairy Duster 1/80, f/16 50mm up close. 50mm 1/640, f/8 No color fringing, sharp everywhere #review

This is the lens version that has an “auto exposure” chip to communicate to the camera, plus a built-in lens hood. The lens is purely manual focus, but auto-focus on a lens this wide would be a bit superfluous anyway (f/5.6 with the scale at about a meter is sharp to infinity). It uses a very sophisticated optical projection formula called “stereographic”, which is extraordinary in a lens of this price. The lens comes in many flavors, including Canon, Sony, Pentax, and Nikon. For some inexplicable reason, the Samyang company calls this lens Rokinon. Even the internal EXIF data for this lens says “Samyang”. Being a fisheye, this lens is very specialized and is an acquired taste (I just cannot resist puns). If you have something like Photoshop or Adobe Elements, then you can use something called “spherize” to largely straighten the rather extreme curved lines without losing the 180-degree field of view. More on that later. Other straightening methods, such as “warp” are also mentioned later, but those techniques will need trimming of the edges, and you won’t end up capturing 180 degrees. If you stick with landscapes and avoid horizon lines, people might not even guess that the pictures were done with a fisheye. See examples below. No single lens can do it all; use the right tool for the right job. First off, promise me that you won’t go taking any pictures of females with this lens. Paraphrasing Hagrid, “they won’t thank you for that”. On the other hand, your rooms will look so huge they’d make inhabitants of Buckingham Palace jealous. You cannot use filters with this lens, so be ready for a bit of a challenge to clean it; the front element is an extreme spherical shape. This is a DX lens; you’ll get a circular image if you try it on an FX sensor camera. Surprisingly, the lens is metal and glass; for its price, you’d expect to see lots of plastic. The lens hood is plastic, though, but not flimsy in any way. The focus ring is rubberized like you’d expect, and has very smooth operation. The lens also has a proper metal lens mount, but no rubber seal. I wouldn’t go out in heavy rain with this baby, but then again I wouldn’t go out in the rain with hardly any of my equipment. The resolution this lens can produce is quite amazing. Just don’t expect that resolution in the corners with the lens wide open. Something I noticed that isn’t quite so nice is that the aperture isn’t entirely accurate. You can get some variation in exposure as you switch to different (small) apertures. The physical area for a given aperture on this lens is incredibly small, given its focal length and is probably very hard to build the mechanics to achieve it precisely. Just be aware of this characteristic. There is also a fairly large amount of chromatic aberration that can be a challenge to control in post processing. The most difficult is the “axial” type; I use Capture NX2 to minimize it. I’d recommend you try out Live View at high magnification to get a feel for how the distance scale on the lens relates to actual focus. My lens has perfect infinity focus when the lens is at the “infinity” hard stop, but at nearer distances the scale differs a bit with reality. This becomes a near “don’t care” when you stop the lens down. What you don’t get: vibration reduction. Not such a big deal on short focal lengths, however. Yes, you’ll get internal reflections to show up when you point it at the sun; they’re generally a pretty small part of the picture, though. It can be difficult to avoid getting the sun in the shot, given the extreme field of view. I didn’t notice any objectional vignetting, which surprised me. Again, take a look at the sample photos at the bottom to see for yourself. Use your favorite image editor to deal with any lateral chromatic aberrations. This is a good video lens, if you don’t get too close to people or pan around too much. If you do pan around too much, your audience will be barfing in the aisles. Although the lens has a computer chip to communicate to the camera, distance information is not properly transmitted and is therefore incorrect in the EXIF data. Rokinon (Samyang) 8mm with fixed lens hood. Looks like 2001 HAL. Distortion Analysis Distortion of the resolution target. Only 18 inches from sensor plane. Same 8mm photo after software distortion correction “spherize -52”. An interesting feature in Photoshop and Elements is “spherize”. It can counteract the distortion to a large extent, although it makes some dog-legs near the frame edges. It maintains the full 180 degree field of view. Other software with more mainstream ‘barrel distortion’ correction only mildly corrects anything, and cuts off the frame edges to boot. But you should be buying this lens BECAUSE it does distortion to get you to 180 degree coverage! There’s also a “warp” feature in Photoshop to help straighten to just about any magnitude you wish, but then you’ll need to crop the borders of what’s left. Lightroom distortion corrections, however, can turn this into a rectilinear super-wide lens that looks quite good. Resolution Testing My goal is to enable you to assess resolution between different lenses in a standard, scientific way. I also give you the information (see my MTF Cliff’s Notes article) to be able to repeat these tests for yourself. The following resolution tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. Resolution measurements are in MTF50 lp/mm. This measurement represents how many image line pairs can fit inside a millimeter before the white-to-black chart transitions degrade to 50%; e.g. “turn to mush”. For me, anything beyond about 30 lp/mm is fine, and beyond 50 is outstanding. Higher-resolution sensors yield higher measurements, much like you’d expect. This is a really tough lens to measure. It drove the MTF Mapper software crazy. Due to the fisheye nature of this lens, I cannot measure right to the corners of the frame. I show some photographs of what the chart looks like below, so you understand what difficulties the measurement process has. Also, the (large) A0 resolution target I used had to be only 18 inches from the camera sensor to fill the frame. As a result, the resolution numbers are for a pretty close focus distance. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in another article, but suffice it to say that this is really great stuff; it’s comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, really knows his stuff. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. The meridional/sagittal differences are what “astigmatism” is all about. This lens is better in the sagittal direction. The meridional direction is terrible until about f/5.6, and it nearly disappears as if by magic around f/8. Strangely, the bad meridional performance at wider apertures was only on the right-hand side of the image, as if the optics were tilted. If it were simply tilted optics, though, then the sagittal values would also have been bad. What the resolution target looks like. Mine is mounted ‘upside down’. Finally, I’m getting around to some actual resolution results. Tests were done with manual focus, IR remote, and a really big tripod. Resolution Results The following measurements need some explaining. The MTF Mapper program has some problems analyzing the whole resolution chart, due to the image distortion. As a result, some of the plots below have a ‘butter fly’ effect. Also, the distortion means that the chart doesn’t extend to the left/right frame edges. This means that there isn’t any “corner” resolution data. First, here are some close-ups showing the meridional-direction problem I spotted. The problems are mostly seen on the right-hand side of the frame. Strange meridional performance at f/3.5 on one side of squares. Meridional performance on frame edge substantially improved by f/8. In the following plots, another anomaly I noted is that the “sagittal” plot indicates a bad center, which is not correct. The center is actually the highest resolution, as can be seen in the “annotated’ resolution chart photos. Frame center is excellent, but MTF Mapper shows it as “bad” sagittal. MTF Mapper doesn’t like the distortion, and won’t measure sections of the frame. Wide open. Meridional is really bad on right of frame. The “butterfly” effect on the sagittal plot is due to the MTF Mapper not recognizing the distorted squares as valid, measurable chart elements. Meridional is still really bad on right of frame at f/4.0 Vast improvement at f/5.6. Even the corners are good. Excellent everywhere at f/8.0 Peak performance at f/11. Impressive at twice the price! Diffraction is setting in, but still good performance at f/22 8mm f/11 NO distortion adjustments. 3-shot HDR using Zoner Pro. 8mm f/11. Again, no distortion adjustments. 6-pointed sunstar. #review

This is the Tokina version that uses the screw-drive for auto-focus. It has the same optics as the newer internal-focus motor “Pro II” version. The newer version also claims to have improved anti-reflection coatings. I have read that some users find the newer “Pro II” to be less sharp than this original version, but I suspect it’s just lens sample variation they’re seeing. I’ll concentrate on the lens resolution performance in this article, in addition to my observations on any unusual behavior I have noted in using it. Some people are averse to lenses that use the “screw drive” focus, but for me it’s basically a “don’t care” when the focal length is small (e.g. non-telephoto). Focus is still plenty fast (camera model dependent) and actually one of my more repeatable lenses for phase-detect focus. An interesting thing I noted on focus is that the “live view” autofocus wasn’t consistent. This is the exact opposite of what typically happens with other lenses, where the “phase detect” is less consistent. I got such consistent results with phase detect that I used it for the resolution tests and got absolutely repeatable results. Since I only have one copy of this lens, I can’t say if you will see this effect or not. Although it’s a “DX” lens, it has full frame coverage on FX at the 15mm-16mm lengths. I’ve read that corners are fairly soft on FX, but I haven’t tested it. Update 6-10-2016: I have tested it on a Nikon D610. It's very good at 16mm, but I don't like the level of vignetting at 15mm. See the my review here. Tokina built this lens for professionals, so it’s a metal and glass hulk. It’s actually quite beastly in size and weight. It uses 77mm filters; I keep a UV filter on it, mainly because the front element is challenging to clean due to its substantial curvature. What you get for that big diameter: f/2.8 and constant-aperture while zooming! What you don’t get: vibration reduction. Not such a big deal on short focal lengths, however. These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. I actually left the UV filter ON for the tests; the filter doesn’t have any measureable effect on resolution results. I’ll let the pictures at the end of this article speak for themselves in regards to the anti-reflection coating and contrast. Yes, you’ll get internal reflections to show up when you point it at the sun; you will get flare when you “provoke it”, so don’t provoke it! The lens also has a proper metal lens mount and gasket (rubber seal). That’s it as far as dust/weather resistance is concerned. I read plenty of complaints about the focal length range only going from 11 to 16. I bought this lens for 11mm, so I really don’t care about how ‘long’ it can get; you’ll have to decide if this is important to you or not. You can bet that a longer focal length range would result in more optical problems. I am very pleased with the optical quality of this lens. It would be nice if the corners were a bit sharper, of course. But when you compare it to the competition, you’ll see that the corner performance is actually first-rate. Note that in the resolution plots below you can get really good corner performance when you stop down. Although this is a rectilinear lens, you’ll notice barrel distortion, particularly at 11mm. Since you can correct it using your favorite image editing software, it’s not a big deal. For landscapes, it is a total non-issue about 99% of the time. I bet you won’t even notice distortion when you get to 16mm. What I didn’t notice was vignetting, which surprised me. Take a look at the sample photos at the bottom. Make it disappear with your image editor if it bugs you; same goes for any lateral chromatic aberrations. This is a really great video lens. If you mess with focus while shooting video, you’ll want manual focus; it works by pulling the focus ring toward you to engage a clutch. I didn’t notice any focus breathing (grow/shrink image size with focus change), either. It also appears to be “parfocal”, so you don’t need to refocus after zooming. Tokina 11-16mm f/2.8 with removable lens hood (plus 77mm UV filter). Resolution Testing This is why you should read this article. My goal is to enable you to evaluate resolution between lenses in a standard, scientific way. I also give you the information (see my MTF Cliff’s Notes article) to be able to repeat these tests for yourself. Resolution measurements are in MTF50 lp/mm. This measurement represents how many image line pairs can fit inside a millimeter before the white-to-black chart transitions degrade to 50%; e.g. “turn to mush”. For me, anything beyond about 30 lp/mm is fine, and beyond 50 is outstanding. Higher-resolution sensors yield higher measurements, much like you’d expect. Before I forget, you will notice a couple of tiny weird blobs in some of the resolution plots that follow. Please ignore these, since they are definitely not a lens imperfection. The measurement software is extremely sensitive, and an imperceptible chart surface indentation shows up very clearly in the measurements. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in another article, but suffice it to say that this is really great stuff; it’s comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, really knows his stuff. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. The meridional/sagittal differences are what “astigmatism” is all about. This lens is decent in the sagittal direction when you get away from the lens optical center. Meridional direction isn’t nearly as good; this is the “norm” in most lenses. The middle of the lens is beyond impressive, as you’ll see. What the resolution target looks like. Mine is mounted ‘upside down’. Finally, I’m getting around to some actual resolution results. Tests were done with phase-detect back-button autofocus, IR remote, and a really big tripod. As I mentioned before, this lens likes phase-detect better than contrast-detect focus. I use the “best of 10 shots”; not every shot gets the identical resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce. MTF Mapper “focus target” plot. Note the “+15” fine-tune for phase detect. Focus fine-tune was set to +15 to calibrate this lens to my D7100. Take a look at my MTF Mapper Cliff’s Notes article if you’re curious about the details. The lens is so wide that I had to have my A0 target at only 1 meter away. Distortion Analysis Worst-case distortion at 11mm showing the resolution target Same 11mm photo after software distortion correction 16mm uncorrected distortion. I don’t see any distortion. Resolution Results The following measurements were done at the extreme focal lengths of the lens. 11mm wide open. Great center, corners not very good. f/5.6 has outstanding center, and now corners are quite good. Diffraction is killing resolution at f/16 16mm wide open. Again, corners aren’t that good yet. f/4.0 has exceptional center, and corners are now fine f/16 and diffraction is again killing resolution f/22: Don’t go there. Sample Pictures Great for emphasizing the foreground. 11mm Drinking Dragon (Los Arcos). 16mm. #review

This article will show the lens MTF50 resolution performance and discuss how well the lens autofocuses. Repetition of the Nikon specifications of the lens will be mostly avoided. This is one of the most popular Nikkor DX “prime” lenses ever produced. It is also one of the most inexpensive lenses; I avoid labelling it “cheap”, since that has a connotation of “low quality”. Nearly everybody will tell you to “just get one”, and with good reason. It’s reasonably fast, focuses well, and provides the natural perspective that equates to the FX “50mm” standard lens. What you don’t get: vibration reduction and great corner resolution. My usual disclaimer: this is looking at a single copy of the lens. Yours will be different, but hopefully ‘similar’. The only place I know of that tests lots of copies of lenses is here . These tests were done using a Nikon D7100 (24 MP) with unsharpened 14-bit compressed RAW format. Here is a link to get pretty good information on this lens. My main complaint with them (and most of the other web sites) is that they simplify resolution measurement down to a single number for an f/stop. It’s not that simple; resolution is a 2-dimensional thing (not to mention directions within those 2 dimensions). The focus ring on this lens is a properly wide one, nearest the filter. Just like their ‘pro’ lenses, you can use it anytime you want to override autofocus. This ring is much better than most of Nikon’s kit lenses that have that skinny plastic thing at the end of the lens. The lens also has a proper metal lens mount and gasket (rubber seal). That’s it as far as dust/weather resistance is concerned. Annoyingly, there is no distance scale. Not a huge problem, but still it should have one. Also note: don’t use this lens for infrared; it produces a nasty hot spot in the middle of the field of view in infrared; Nikon’s (even less expensive) 50mm f/1.8 AF-D lens in comparison is wonderful when shooting infrared, and it also is an FX lens. As an aside, Nikon’s 18-55 various kit lenses are all very good at infrared. Nikkor 35mm f/1.8 DX AF-S with included hood Autofocus Fast, repeatable, silent. Enough said. All of my lenses need some focus fine-tune calibration; so does this lens. Vibration Reduction (VR) Nope. Helps keep this lens inexpensive. Even Nikon’s 85mm f/1.4 AF-S doesn’t have VR. Just saying. Resolution Testing This is why you should read this article. I won’t mention “good”, “fair”, “excellent” or “blur units” to interpret resolution. I promise. My goal is to enable you to evaluate resolution between lenses in a standard, scientific way. I also give you the information (see my MTF Cliff’s Notes article) to be able to repeat these tests for yourself. Resolution measurements are in MTF50 lp/mm. This measurement represents how many image line pairs can fit inside a millimeter before the white-to-black chart transitions degrade to 50%; e.g. “turn to mush”. For me, anything beyond about 30 lp/mm is fine, and beyond 50 is outstanding. Higher-resolution sensors yield higher measurements, much like you’d expect. Before I forget, you will notice a couple of tiny weird blobs in some of the resolution plots that follow (along the top edge). Please ignore these, since they are definitely not a lens imperfection. The measurement software is extremely sensitive, and an imperceptible chart surface indentation shows up very clearly in the measurements. I guess I’ve been doing too many tests and will soon have to retire this chart. I use a (free!) program called MTF Mapper from here to measure lens resolution. The download site also has files for printing out the resolution targets (mine are A0 size on heavy glossy paper (‘satin’ finish seems to work just as well), dry-mounted onto a board). This program is covered in more detail in another article, but suffice it to say that this is really great stuff; it’s comparable to ‘Imatest’ in the quality of the MTF measurements, and it uses the “slanted edge” technology similar to ‘Imatest’, also. The author of MTF Mapper, Frans van den Bergh, really knows his stuff. Visit his site and give him the praise he deserves. The chart design used for resolution tests orients all of the little black squares to be ‘slanted’ but they’re generally aligned in meridional and sagittal (think spokes on a wheel) directions to correlate better with the usual MTF plots you’re familiar with. There’s often a dramatic difference in sharpness between these two directions, and the chart photographs show it clearly. The meridional/sagittal differences are what “astigmatism” is all about. This lens is decent in the sagittal direction when you get away from the lens optical center, and corners are “okay”. Meridional direction is a less rosy proposition, but judge for yourself in the ensuing resolution plots. The middle of the lens is impressive, as you’ll see. What the resolution target looks like. Mine is mounted ‘upside down’. At long last, I’m getting around to some actual resolution results. Tests were done with “Live View” AF-S autofocus, contrast detect, IR remote, VR OFF, really big tripod. That’s how I get around any phase-detect problems with focus calibration. The results don’t seem to improve using manual focus and 100% magnification in Live View, so I don’t bother. I use the “best of 10 shots”; not every shot gets the same resolution results. All cameras operate on the “close enough” principle for focus, so many tests are needed to determine the best resolution that the lens can produce. Small resolution chart imperfection on top edge; please ignore. Diffraction is exacting its toll at f/16. Sample Pictures Pumpkins that look amazingly like a tiger Panorama from 5 vertical-format shots stitched using the Hugin program #review