Optars are only common in the US and on Graflex cameras, there were far more 135mm f4.7 Xenars made.
Originally Posted by jp498
The only problem with both lenses is they have very little coverage and allow very little in terms of movements, not quite so important on a Crown or Speed Graphic. I used a pre WWII 135mm f4,5 Tessar on my Crown Graphic for a year before replacing it with a 150mm f4.5 T (coated) CZJ tessar. The other issue is the edges and corners of these lenses are only really sharp at f22. I do use a 135mm f4,7 Xenar..