Aperture on Tele-Xenar 4/135 does not open all the way - why?

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xtam667 Regular Member • Posts: 177
Aperture on Tele-Xenar 4/135 does not open all the way - why?

I have got this vintage Schneider-Kreuznach lens in DKL mount. I push the aperture lever to the max but the aperture does not open all the way like in any other lens I have seen:

This is supposed to be the f4 max aperture on a 135mm lens

What is with this lens? It is near mint and the aperture lever and focusing ring work fine. Another thing I noticed is that it closes to a much smaller opening at f22 compared to another 4/135.  A mystery to me given how good the condition of the lens is and apparently working as intended.

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