Olympus Zuiko Auto-W 21mm f/3.5

It is rectilinear, not a fisheye, so the walls bow in a clean, predictable way rather than wrapping. For a 21mm of this period that is the honest starting point, and this little Zuiko shows the simple barrel distortion typical of a fast wide of its era, noticeable enough that a building shot face-on will want a quick correction pass before the verticals read true. The good news is the bow is the easy kind to fix in software, with no smearing in the corners to fight. It is sharp in a way the modest f/3.5 aperture does not advertise. Stopped to f/8 the field is even nearly corner to corner, contrast is crisp, and the drawing is clean and undramatic. People underrate it precisely because it sits in the shadow of the f/2.

That shadow is the real context. Olympus built two 21mms for the OM system. The f/2 was Maitani's flagship statement, the first 21mm to reach f/2, and it now trades in the four figures because the cine crowd rehouses it for its sharpness and character and the matched f/2 aperture shared across the OM primes. This is the other one. It came first, in 1972, a genuinely compact wide that disappears on the front of an OM-1, and it does the unglamorous job of being optically very good for a fraction of the money. Where the f/2 is a collectible, the f/3.5 is a working lens you can still buy without flinching.

Wide open it is honest. The center is already sharp at f/3.5, the corners trail a little and the extreme edges soften, but by f/5.6 the frame has pulled together and by f/8 there is nothing to complain about. Flare resistance is acceptable rather than a strength, and it is the early single-coated version's known soft spot; the later multicoated glass copes better with side light and window light, and a bright source dead in the frame can still throw a ghost or a little veil. Color is neutral. There is no swirl, no nervous bokeh, because at 21mm and f/8 bokeh is barely a conversation. This lens is about the whole frame being in focus and being rendered without fuss.

So it lives where deep-focus wides live. Landscape, travel, architecture, cramped interiors where you cannot step back and need the bowing to stay correctable. It is the 21mm you put on the camera for a day of walking and forget about, because it weighs almost nothing and the 49mm filter thread takes the same cheap screw-in filters as half the rest of the OM kit. That thread matters in the field: a graduated ND or a polariser on a 49mm ring costs a holding back on the meter, and Zone Light Meter folds the filter factor into the reading so your highlights land where you placed them instead of two stops hot. A 21mm exaggerates sky, so you will reach for that grad more than you expect.

The honest weakness is the speed. At f/3.5 it is a daylight and tripod lens, not a low-light tool, and if you need to shoot wide open in a dim room the f/2 sibling exists for exactly that reason and charges you accordingly. One thing to know when buying: the early single-coated G.Zuiko and the later multicoated MC version share the same seven-element formula, so the optical drawing is the same and the difference you are paying for is the coating, not the glass. None of that dents the case for it. As a sharp, pocketable super-wide for landscape and travel whose distortion corrects out in a click, this is one of the quiet bargains of the OM mount, and it stays that way because everyone is busy looking at the f/2.