Olympus Zuiko Fisheye 8mm f/2.8

Stand in the center of a circular plaza, aim straight up, and this lens hands you the whole dome of the sky as a single disc, the horizon running all the way around the rim. A rectilinear ultrawide cannot do that. Even a diagonal fisheye like Olympus's own 16mm only gives you 180 degrees corner to corner, cropped into a rectangle. The 8mm is a true circular fisheye: 180 degrees in every direction, projected as a circle of image floating in black on the 35mm frame. And it did it at f/2.8, fast for a circular fisheye where most rivals sat at f/5.6 or f/8, with Nikon's 8mm f/2.8 the main exception in the same class.

Optically it is a retrofocus design built around a hugely curved front element that bulges out past the barrel, the only way to clear an SLR mirror at this angle. Focus is almost a formality. Depth of field at 8mm runs from a few centimeters to infinity, so you set it and forget it. Distortion is total and entirely the point: every line that does not pass through dead center bows into an arc, and the closer to the rim, the harder it bends. The middle stays crisp while the outer edge of the circle smears, the way every fisheye does. What the f/2.8 buys you is handholding in dim interiors, where a slower circular fisheye would keep you bolted to a tripod.

People bought it for specific jobs. Meteorologists and astronomers ran circular fisheyes in whole-sky cloud and star cameras. Architects shot interiors too tight for anything else. The 1970s creative crowd loved the round-window look for album sleeves and posters. Today it is mostly OM-system collectors and the occasional artist who wants the circle baked into the negative instead of faked in software.

The honest problem is that it is a one-effect lens, and the effect tires fast. The circular crop throws away most of the negative, your own feet and shadow creep into frame constantly, and there is no front filter thread because nothing threads onto that dome, which is why the spec lists none. It is also among the priciest lenses in the OM catalog, comfortably four figures, while a modern Sigma 8mm gets you ninety percent of the look for a tenth of the money. You pay the Zuiko premium for the f/2.8 and the badge.

One metering caution. A 180-degree frame takes in the bright sky and the dark ground in the same exposure, so an averaged reading splits the difference and you lose one end or the other. Meter the zone you actually care about. Spot the foreground or your subject in Zone Light Meter, place it where you want it, and let the sky fall where it lands.