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Nikon Nikkor 20mm f/4 AI. You may be able to get it used here. Introduction This is one of my favorite Nikkor lenses. Galen Rowell's, too: he raved about it in the September 1999 issue of "Outdoor Photographer" magazine. Why? Simple: It's optically better than the 20-35mm f/2.8 zoom many professionals lug around, and its one of the tiniest lenses Nikon has ever made. Size is very important to those of us who actually take our equipment with us when we travel. This lens is a little hard to find; Nikon only made it from about 1977 through 1978. Here is an article about its development. It was quite revolutionary and resulted in patents for its innovative design. Specifications This tiny jewel has 10 elements in 8 groups. It's just 1.8" (47mm) long by 2.5" (63.5mm) in diameter. Yip, it's less than two inches long, smaller than a 50mm lens and easy to loose in a big pocket. It only weights 7 oz. (210 grams). It has a seven-bladed diaphragm that stops down to f/22. It focusses down to 0.3m or 1 foot. Hood: HN-14 screw-in metal, or bizarre HK-3 slip-over metal hood. The HK-3 is weird because it slips over the focus ring and holds on with a compression fitting! You can ignore the hood. The filter threads provide about the same degree of stray light protection as the hood. Either tiny hood doesn't improve anything; unlike the 15mm f/3.5 AI-s this lens thankfully has few ghosts or flare problems, so you luckily just don't need a hood. Performance I have no vignetting problems when used with a Nikon brand 52mm filter. You may run into trouble with other brands like B&W, Tiffen and Hoya who use thicker mounting rings. It has the usual Nikon wide-angle barrel distortion at all distances, which is hidden through the viewfinder by the complementary pincushion distortion designed into many Nikon viewfinders. On a DX digital camera, it is first-order distortion, easy to correct in Photoshop CS2's lens distortion filter with a setting of +2.5. The maximum aperture is really closer to about f/4.5. Don't worry, the metering system compensates for all this. By cheating a little like this Nikon was able to get stellar performance in this tiny lens. It does have very few magenta ghosts if you get the sun in your image. There is a little lateral yellow/blue chromatic aberration visible in the lab. Performance by aperture: I get very good performance even at f/4. I use it at any aperture, I see very little sharpness variation with aperture. f/4 great in center,
mild coma in edges but mostly lateral color. Some light falloff Recommendations As stated above, if you don't need AF then this is your lens. It's the sharpest 20mm I've used, although that may be to the luck of the draw. This lens also showed me the complete lack of correlation between appearance (what camera dealers call "condition") and performance. I have had two of these lenses. The first one I bought used for $300 from a prominent Palo Alto, CA dealer. It looked completely unused. Its performance was worse than the beat-up one I use today as pictured above. The lens I use today looks much more beat up and cost me only $150 from a stranger. It performs much better. These differences are due to manufacturing variations. The only way to see how well a lens works is to photograph with it. Luckily the dealer who sold me the nice looking but poor performing 20mm took it back. That's why I always buy from dealers with a liberal return policy. I can handhold it with sharp results 70% of the time at 1/8. It's always sharp for me at 1/15. |
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