Carl Zeiss Biogon T* 21mm f/2.8 G

There is a particular kind of photographer who carries this lens: someone with a Contax G2 slung over one shoulder, walking a city grid at dusk, shooting buildings dead straight because they know the verticals will stay vertical. The Biogon 21mm is the reason that camera still trades for real money. People buy the whole G system to get access to this single piece of glass.

A Biogon is a near-symmetrical wide-angle, not a retrofocus, which means the rear element sits very close to the film plane. On an SLR you cannot do this because the mirror needs room, so SLR 21mm lenses are retrofocus Distagons that fight distortion and corner falloff. The Biogon does not fight anything. Straight lines come back straight, and distortion is so low it is effectively a non-issue for architecture. Because the design isn't wrestling a retrofocus geometry, the corners hold up wide open better than most SLR 21mm glass of the era managed. The center is razor-sharp at f/2.8 and the corners are already good for a 21mm, then the whole frame snaps even by f/5.6 to f/8.

Color and contrast are the Zeiss T* signature: deep, slightly cool, with real separation in the shadows and no haze veiling the lower tones. Flare resistance is excellent for such a wide lens, partly because the multicoating is genuinely good and partly because there are not many air-to-glass surfaces throwing light around. Bokeh barely enters into it. At f/2.8 and 21mm almost everything is in focus, and that is exactly what landscape and street shooters want.

Where it bites you is the system, not the optics. The Contax G is an autofocus rangefinder, and at 21mm the in-finder framing is approximate enough that Zeiss shipped a separate accessory optical viewfinder for the hotshoe. You compose in that, focus with the body, and trust it. People who came from manual Leica wides find the workflow strange. The other honest limit is vignetting wide open, mild but present, the usual tax on a symmetrical wide.

It sits in an odd spot now. The film bodies are aging and the lenses cannot be adapted cleanly to most mirrorless cameras because that deep rear element clips sensor stacks and smears the corners on digital. So it stays a film lens, cross-shopped against the Leica 21mm Elmarit by people who want the rendering without the Leica price. It is still one of the best 35mm wide-angles ever sold, and the resale holds because nobody is making symmetrical 21mm glass anymore.

One metering note. With the 55mm filter thread you can run a screw-in ND grad to hold a bright sky over a dark foreground, which is exactly the situation a 21mm landscape frame creates. Meter the foreground and the sky separately, set your grad strength to the difference, and let Zone Light Meter place your shadows where you want them rather than letting the bright top of the frame pull the reading flat.