I'm considering buying an older 28mm LTM lens for occasional use on my Canon bodies. Of the affordable (i.e., non-Leica) options, is there any dramatic difference between the Canon (f/3.5 and f/2.8), Avenon/Kobalux (f/3.5), W-Komura (f/3.5), and Orion-15 (f/6)? Or are they close enough in performance that I should simply purchase based on condition?
Take this with a grain of salt because I don't have any of these lenses, but I remember from doing my research on them that the Avenon is much bigger than the others and the Orion has least distortion. I ended up buying a Voigtländer Ultron 28 f/1.9, that's another candidate for you to consider. Be warned, many have haze. Other than that, it's a technically very competent modern lens with an aspherical element, likely higher resolving than all these older lenses.
I had the Canon 2.8, sharp at 2.8, really sharp at F 8 to 11, very little distortion as well. But as noted above a much newer Voigtlander will have better coatings, the aspherical element color will be better if you shoot much color. If very occasional based on price would go with the 3.5.
I've used Elmarit 28 (several), the Voigtlander 28mm f3.5, and currently have the Canon 28mm f2.8. I prefer the Canon image character to that of the modern Voigtlander. The Canon is small and handles well. I think it makes a classic match with the Canon body. Years ago i also owned the Canon 25mm which is also worth consideration if the wider view suits your taste.
I know, not “older” but I would (actually I will) use this unique moment in time where there’s actually a 28mm LTM in current production - and get the current Voigtlander 28/2.8 L39.
I have both. Of my two examples, both the cannon 28mm lenses are sharp in the center at their widest aperture.
I would not hesitate to use either one. But the f2.8 is better at the edges until you stop down to about f8.
Also consider the Nikkor 2.8cm f3.5, and the new Voigtlander 28mm.