Pentax SMC Pentax-FA 77mm f/1.8 Limited (K)

Put the FA 77mm next to the lens everyone else reaches for at this length, an 85mm f/1.4, and the Pentax loses on paper and wins on the print. It is shorter, slower to focus, and gives up part of a stop. Then you shoot a face with it and the 85 looks like a tool while the 77 looks like a choice. People who own one rarely sell it, and the ones who do tend to buy it back.

The number itself is the first tell. 77mm is not a round focal length anybody specs for marketing. The story is that the team did not design this lens to test well; they judged it by how its prints looked rather than by what a chart measured, and the odd focal length and the f/1.8 aperture fell out of that approach. Wide open at f/1.8 the center is sharp while the corners stay soft and distant detail goes a little gentle, the result of a deliberate field curvature that trades flat-field crispness for very low astigmatism and almost no color fringing. Stop down to f/2.8 and on to f/4 and the whole frame tightens up cleanly. The out-of-focus rendering is the signature: smooth and neutral, low on nervous edges, with the corners staying soft and calm rather than swirling. Backgrounds fall away instead of breaking up. SMC stands for Super Multi Coating, and it earns the name. Flare resistance shooting into a low sun is better than a lens this old and this fast has any right to be.

The build is part of the appeal and not a footnote. This is a machined aluminum barrel, a real metal focus ring with a long throw, and a clicking aperture ring that still matters on film bodies and on the K-mount digital cameras that kept it alive for two decades. It drops onto any Pentax K-mount body, with aperture-ring operation on the early mechanical cameras from the 1970s and full autofocus coupling on the AF film MZ line and every modern Pentax K-mount DSLR that came later. The 49mm filter thread is small and cheap to fill, which matters if you want a polarizer or a soft grad on it for outdoor portraits.

Who shoots it: portrait and available-light people who care more about how skin and hair render than about MTF charts, plus a stubborn population of Pentax loyalists who bought into the Limited line and never left. This is a lens whose cult has survived Pentax passing from Asahi to Hoya to Ricoh, which is more corporate turbulence than most optics live through. On a 35mm body it is a classic head-and-shoulders length. On APS-C it becomes a tight 115mm-equivalent, useful but cramped for environmental work.

The honest weakness is the autofocus. It is screw-drive, it hunts in dim light, and it is audibly slow next to anything ultrasonic. For static subjects this is a non-issue. For a moving kid at f/1.8 you will miss frames. Most owners learn to focus it by hand and forget the motor exists.

It has never been cheap and used prices have crept up rather than fallen, a rare thing for a lens this old. People cross-shop it against the FA 43mm Limited and against fast 85s from other systems, and the ones who buy it are buying the rendering, not the spec sheet. One practical note: wide open in a dark room is where this lens lives, so meter for the shadow you actually care about and let the falloff do its work. In Zone Light Meter, place your reading on the zone you want held and the f/1.8 maximum aperture is right there in the calculation.