Vivitar sold several 28mm f2.8 lenses with a Canon FD mount over the years. They were made by different lens manufacturers at different times and produce different results. Probably the best is the 28mm f2.5, made by Kiron with serial numbers starting with 22XXXX. It is larger and heavier than the others and has a 67mm filter thread.
I had a Vivitar 28 2.5, in Nikon non AI, mount, found it at yard sale in the late 70s, I shot few rolls with it, IQ was pretty good. As I had a Nikon with the standard 52mm filter thread I gave it to a friend who's gear had gone up in a fire and was cobbling togeather a kit while he waited on an insurance settlement.
I agree with you Paul, I currently own three FD " L" lenses that at the time they were manufactured about forty years ago I couldn't afford, but I remember in those days they were at the cutting edge of lens technology, that was way ahead of all the other major leading lens manufacturers, and even Nikon made nothing like them.
Reading around the Canon Museum site, the design goals of the FD lenses read like a roadmap to outdo Nikon in lens design. They succeeded with the 50/1.4 FD, it's noticeably more "alive" than the contemporary (1971) Nikkor S - 50/1.4 at wide apertures.
Canon Camera Museum - https://global.canon/en/c-museum/history/story05.html scroll down about half way in the period 1970-75.
Reading around the Canon Museum site, the design goals of the FD lenses read like a roadmap to outdo Nikon in lens design. They succeeded with the 50/1.4 FD, it's noticeably more "alive" than the contemporary (1971) Nikkor S - 50/1.4 at wide apertures.
Canon Camera Museum - https://global.canon/en/c-museum/history/story05.html scroll down about half way in the period 1970-75.
I don't think any other manufacturers in the early 1980s were using the low dispersion glass that Canon used in their "L" range of lenses and also aspherical lens elements.to enable the optics to provide good quality images at large apertures.
Vivitar sold several 28mm f2.8 lenses with a Canon FD mount over the years. They were made by different lens manufacturers at different times and produce different results. Probably the best is the 28mm f2.5, made by Kiron with serial numbers starting with 22XXXX. It is larger and heavier than the others and has a 67mm filter thread.
To give credit where credit is due, Petri made some great cameras like the Color 35 (an improved Rollei 35), and the half-frame Junior (AKA, Compact, Half & Dejur).
I had the Colour 35 and it gave nice photos when care was take to photographic basics.
I might like to shoot one again, but this time use b&w colour contrast filters, where when I was very young with my first real 135, the Petri, I used non.