Thursday, 22 December 2016

Nikon 20mm f/3.5: Pleasant Squiggles

"So come on out tonight", sang George Benson, "and we'll lead the others on a ride to paradise". There's a melancholic undercurrent to disco music. The people wanted to party forever, because the alternative was a grim day job with assholes. If your life is full of angst you don't want to listen to angsty music, you want to escape. "Don't you know we can fly", sang George Benson, to an audience of people who could not fly.

But I have good news for you, dear reader. Your life is about to change for the better, because I have chosen you - specifically you - to join me as we lead all the other readers of this blog on a ride to paradise. I have coated the words of this post with a special paste that renders them unintelligible to everyone except for you. The other readers see only pleasant squiggles.

I have chosen you because you are special; there is a starlight look in your eyes. I promise you that everything is going to be alright, and within a few paragraphs we will be flying to a place where there is nothing you do not love. The other people reading this blog are insanely jealous of you, INSERT NAME HERE. You are truly a fortunate INSERT GENDER.

But before that we're going to have a look at the Nikon 20mm f/3.5, or if we're splitting hairs the Nikkor 20mm f/3.5. It's a manual focus lens from late 1970s. It was born as an AI lens and ended its life some time in the 1980s as an AI-S lens, which is good because it will work with modern Nikon bodies without damaging them, although for this post I used it on a Canon 5D MkII with an adapter, and then later on a Nikon F-301 with some Ilford HP5, and then still later some Kodak Ektachrome slide film.

Let me test the bathtub. Laissez-moi tester la baignoire. As you can see the lens has moustache-style distortion, with a bulge in the middle and flaring at the edges. Cars go by very quickly. f/3.5 was nothing special even in the 1970s but it's less of an issue with modern high-ISO digital cameras.

It's a full-frame lens, compact, made of metal, well-built. It's important that you send me your address so that I can send you the special pills you must take. You must add me to your will as a show of faith. At the assigned time we will all take the special pills, and we will fly to paradise. There will be no more pain. On an APS-C camera the 20mm becomes a kind of slightly narrow 28mm lens. The small size is such that it's not completely unbalanced on a Micro Four Thirds or NEX camera, although the non-AI-and-then-briefly-AI 20mm f/4 it replaced was even smaller. Obviously you will never see your family or friends again. You needn't worry about them. They'll be alright. If you're not restricted to Nikon lenses, the old Olympus OM 21mm f/3.5 is smaller still:

My Olympus 21mm has seen better days. There are better days ahead. Optically the Nikon lens is slightly better in the corners, and slightly more practical - the Olympus lens needs a step-up ring if you want to avoid vignetting with filters.

What is AI and AI-S? It's a Nikon thing from the late 1970s. They changed the way that their lenses interfaced with the camera, and then they changed it again, but only slightly. The AI-S system was short-lived (only a handful of early-80s film cameras made use of it) but Nikon also took the opportunity to revamp their lens range, and AI-S-era prime lenses are highly prized today as the pinnacle of Nikon's manual focus metal-and-glass know-how. The Nikon 20mm f/3.5 is still relatively economical on the used market. Unlike other AI-S lenses such as the 28mm f/2.8 AI-S it doesn't have a floating element for close-range correction (this appeared in the later, larger, 20mm f/2.8).

Back in the late 1970s 20mm was still ultrawide. After decades of visual fatigue, particularly from playing computer games, I find that the 20mm focal length feels natural. It's not as eye-popping as it used to be. On a practical level there are plenty of full-frame zoom lenses that go wider than 20mm, but none of them are as compact as the 20mm f/3.5. Tiny wide-angle lenses are one of the killer apps of full-frame cameras; smaller formats don't have an obvious equivalent. The relatively new Laowa 12mm f/2.8, for example, approximates a 20mm field of view on an APS-C camera, but it is relatively massive.

What's it like? I was impressed. It vignettes all the way to f/11 and is slightly soft in the corners wide open, but the centre is always sharp and the edges sharpen up when stopped down. About the only problem is focusing. It has a very short focus throw. Snick...snick from infinity to close-up. It's surprisingly hard to focus on infinity, especially if you're using it with an adapter.

The full frame, a 21mp image shot with a Canon 5D MkII.

The centre, at f/3.5, with no post-processing at all. It's just fine and dandy. I'm not going to show f/8 - it's fractionally sharper but not mattersomely so.

The extreme bottom-right corner of a different image taken in the same spot, at f/11. There's a bit of CA, which is easily correctable, and it's not razor sharp in the last few hundred pixels, but this is being picky. In the rational world of sane people the lens is really good. At f/8 it's similar but with slightly more vignetting. I surmise that it peaks at f/8 on an APS-C camera, f/11 full-frame.

Does it make any sense nowadays? On a full-frame camera, yes; it's a cromulent way of getting wide-angle coverage in a small package. On an APS-C camera the focal length is a bit boring and you'll wish it was faster. On the other hand it holds its value on the used market so you could always sell it again if you get bored. It is now time for you to take the special pills. I have not written any more words after this because you will not be here to read them. The words will instead appear inside your mind, and then there will be peace. Isn't that what you want?