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© 2008 KenRockwell.com
Nikon Nikkor 20mm f/3.5 AI. enlarge. You may be able to get it used here. NEW: How to Use Ultrawide Lenses 11 August 2008 January 2008 More Nikon Reviews Introduction top Intro Specifications Performance Recommendations This is a great unknown lens made only for a few years around 1980. Besides being super small and taking standard small 52mm filters, it has excellent optics and superb mechanics. It works wonderfully on the Nikon D3. This was the "cheap" 20mm lens compared to the larger 20mm f/2.8 AI-s back in the 1980s. The sharpness of this f/3.5 is at least as good, and the tiny size and common filter size makes it preferable. It has the same distortion as all the other Nikon 20mm lenses I've tried.
Nikon 20mm f/3.5 AI at f/5.6. Compatibility On the D2, D3, D200, D300 and F6, use the "Non-CPU Lens Data" menu option to input 20mm and f/3.5. This gives full matrix metering and EXIF data, and finder read-out of set aperture. It works great in aperture-preferred as well as manual modes on these cameras. It won't couple well to the cheaper digital (D80 and below) and cheaper film cameras (N80 and below). It works perfectly every professional film camera (F, F2, F3, F4, F5, F6), with Matrix metering on the FA, F4 and F6. See Nikon Lens Compatibility for details on your camera. Read down the "AI, AI-s"column for this lens. Production History This AI lens was introduced in the fall of 1977 as one of the first AI lenses. The optically identical AI-s version replaced it in the fall of 1981. The AI-s version was made until about 1984, since most people preferred the f/2.8 and bought it instead. Nikon made about 30,000 of each version, or 60,000 total.
Boring Example Photo: Hotel. 20mm f/3.5 AI, f/11 at 1/125, Nikon D3, ISO 200. Specifications top Intro Specifications Performance Recommendations Name: Nikon calls this the Nikon Nikkor 20mm f/3.5 AI. Focal Length: 20mm. Used on a DX camera it gives angles of view similar to what a 30mm lens would give on an FX or 35mm film camera. See also Crop Factor. Optics: 11 elements in 8 groups. That's a lot of tiny, precision glass. Multicoated. Traditional spherical design. Diaphragm: 7 blades, stopping down to f/22. Close Focus: 1 foot (0.3m). Maximum Reproduction Ratio: 1:10.8. Depth-of Field Scale? YES. Infra-Red Focus Index? YES, just below the f/3.5 depth-of-field index. Filter Thread: 52mm. Size: 1.624" extension from flange (focused at infinity) x 2.459 " diameter (41.26 x 62.46mm), measured. The widest thing is the aperture ring. Nikon specifies 50.5 x 63.5mm Weight: 8.195 oz. (232.3g), measured. Nikon specifies 235g. Hood: HK-6, which isn't needed and is a pain to attach with a friction gismo.
Nikon 20mm f/3.5 AI at f/5.6. Performance top Intro Specifications Performance Recommendations Overall Performance is great: it's sharp, tiny and just works. Falloff (dark corners) It's got the usual falloff at full aperture. Stop it down an stop or two and it vanishes. Even though I exaggerate it below with flat-field tests, it's only visible in photos at f/3.5 and f/4. Stop down to f/8 and it's gone for normal photography.
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Focus Manual focus has the exquisite classic Nikon feel, which is duplicated nowhere else. One light fingertip is all that's required to focus. The AI-s version focuses with a smaller turn of the ring, while the AI version here spreads the focus range over a larger area to allow more precise focus, depth-of-field calculation and more precise distance markings. AI version focus scale markings: Feet: 10, 5, 3, 2, 1.5, 1.25 and 1 foot. AI-s version focus scale markings: Feet: 5, 3, 2, 1.5, 1.25 and 1 foot. The AI-s version doesn't have the 10 foot or 0.35 meters markings, and replaces the 1.5 and 3 meter markings with a single 2 meter mark. Ghosts It has very few ghosts when pointed into the sun; a hair less than the 20/4 AI. Distortion
Wall of Shame, shot on FX, uncorrected. Note slight wiggling along top. Distortion is complex on film and FX. It's simple barrel distortion on DX, no wiggling. You may as well leave it along on film and FX, since the correction below doesn't do much to eliminate the complex curve. On DX, it corrects perfectly, but why use this 20mm lens on DX when the 18-55mm AFS kit lens works so much better? Plug these figures into Photoshop CS2's lens distortion filter to correct the distortion. These aren't facts or specifications, they are the results of my research that requires hours of data collection and computation.
© 2008 KenRockwell.com *Wiggling, or waviness, remains. Color Rendition Like all Nikon multicoated lenses, I've never seen any variation between any of them in color rendition. They all look the same, the hallmark of a well-designed lens line. One weird thing I see in this lens, as well as other ultra-wide lenses for every brand and format, is a variation of color balance with angle! Look at the boring wall above. It's pinker in the middle, and greener in the corners. Except for this shot of a wall, for which only an idiot photographer would use a 20mm lens instead of a 105mm Micro, I've never seen this effect affect any real photos, like the one at the top of this page. While I also see it on my 75mm Super-Angulon when shooting tests of walls, it never effects real photos. This effect is an artifact of lens coatings. Coatings work based on interference patterns between various wavelengths (colors) of light and the thickness of the coatings. When light comes at an angle other than 90 degrees normal to the glass surface, the light has to travel through more coating, which moves the effects of the coating to longer (redder) wavelengths. Think I'm kidding? Look at the reflections in the glass from the front of the 20mm f/3.5, then move the lens to change the angle. I see many green reflections straight-on, which turn to magenta at an angle. This means less green light gets in at the center (since it's reflected more), and more green gets in at the sides. These reflections are less than 1% of the light, but that means that transmission might vary from 100% down to 99%. I can't see this in real photos. If it bothers you, get the 14-24mm f/2.8 AFS, which has this effect under better, but not complete, control. Lateral Color Fringes on the D3 None. Manufacturing Variation My first sample in the 1990s was softer on one side than the other. The sample I bought in 2007 is fine. Mechanics and Construction The Nikon 20mm f/3.5 is made like they used to. It is built to the highest mechanical standard I have ever experienced. Filter Threads: Metal. Barrel: Metal. Focus Ring: Metal, rubber covered. Aperture Ring: Metal. Finish: Black enamel over black anodize. Mount: Chromed brass. Internals: Metal. Markings: All engraved and filled. Noises when Shaken: Clicking from the diaphragm blades. Sharpness Like most lenses, the sharpness of images made with the Nikon 20mm f/3.5 is more a function of the photographer's skill than any limitation of the lens. On full-frame digital and film, it's soft in the corners wide open, so don't do that if you're shooting test charts. If you are shooting charts, get the 14-24mm f/2.8 AFS, which is superior. I'd never notice any difference between this and any other 20mm lens in real shooting. Sharpness on the D3 full-frame camera viewed at 100% on-computer: In the center, out to an radius of about 12mm, it's perfectly sharp at every aperture. Of course diffraction limits sharpness at f/11 and smaller. In the far sides of the full FX frame (18mm radius), its softer wide open at f/3.5, and becomes s sharpest at f/11. In the farthest corners (a radius of 21.6mm), It's soft wide-open, and sharpest at f/22. I'd shot it at f/11 for best results, or simply not worry about it. it works well at every aperture in the conditions you're likely to use it. Use with Filters There is no problem with vignetting with 52mm filters, so long as you use Nikon brand filters which have very thin mounts. The very thick mounts of Tiffen, Heliopan and B&W filters may cause some vignetting on film and FX digital. If you, as I, want to use colors of filters that Nikon does not make, then I suggest getting a huge filter like a 77mm and using a step-up ring. I use this trick with my 20mm f/2.8 AF and it works fine, even with stacked filters.
Nikon 20mm f/3.5 AI. Recommendations top Intro Specifications Performance Recommendations Definitely get one of these if you want a tiny 20mm lens for film or FX digital. Skip it for DX digital since there are better lenses cheaper, for DX. The older 20mm f/4 AI is as good or better, too. |
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