I've discussed many of the Olympus Pen FT half frame lenses that I enjoy using but I've mostly glossed over one. It's the 20mm f3.5. When I used it on its intended half frame Olympus film camera my results were always hit and miss. Mostly it looked soft and mushy. I had better options among the autofocus lenses that came along with each generation of m4:3 lenses. The poor 20mm just basically got side-lined.
But I am nothing if not persistent. I decided to give it one more try on the front of my favorite photo camera, the G85. The Olympus Pen FT 20mm lens is from about 1968 and was the widest focal length lens made for the half-frame cameras (which have a crop factor of 1.4 with ff 35mm and 2.0 with m4:3).
Each newer generation of Panasonic G cameras seems to be getting better and better at implementing focus peaking. And it's getting easier and easier to enable focus magnification while manual focusing.
This is all good for older, manual focusing lenses.
As I walked around and shot frame after frame with the G85+20mm f3.5 combo I came to realize just how tricky it was in the pre-EVF days to really focus a slow, wide lens accurately. The visual depth of field on a focusing screen seems to obscure the real limits of the "in focus boundaries."
No matter how much I love to romanticize older lenses there is a basic fact that their maximum aperture performance falls behind that of more modern lens options. With that in mind I mostly shot the lens at f5.6 since stopping down nearly always improves the performance of any older lens; up to a point.
When I returned to the studio to evaluate the lens' performance I noticed several things. First, the lens is not particularly sharp wide open and also shows some green and magenta fringing at tonal junction points. Stopping the lens down gains sharpness but it's the old fashion sort of sharpness formula that combines lots and lots of resolution but at a lower contrast and acutance than any modern lens. It's a good candidate for post production, with an emphasis on a good sharpening routine coupled with a liberal use of the clarity slider to add back contrast and edge snap.
Unlike software corrected wide angles of the present the lens is much better corrected for geometric corrections right out of the box. It had to be; there was no firmware correction available when it was designed and sold.
If you go into this lens with the idea of using it for substantive work you'll need to be comfortable shooting either at f5.6 or f8.0 with m4:3 cameras. Those are the sweet spot apertures for this lens. I should also note that it amply covers the APS-C format as it was originally designed to cover the wider (1.4x crop) area of the half frame film cameras. With a decent adapter and with the caveats I mentioned above it should work well on any of the Sony APS-C mirrorless cameras. It may even cover the full frame, but only at the closer focusing distances.
In all, I like the lens for photographs of people and may use it for something but I'm being progressively spoiled by the wide open clarity of lenses like the Olympus 12-100mm f4.0. It's harder now to rationalize using some of these older wide angles on the smaller format cameras when there are so many better modern alternatives. But it's fun to see that it's still highly usable on the latest cameras. Nice delayed obsolescence.