Schneider 58mm XL with diaphragm slightly closed at max aperture

Yesterday I received an Ex+ copy in Copal 0 shutter from KEH. The aperture scale goes from f/5.6 to f/32, but I can move the aperture selector further left or right of the scale. What surprised me is that, when I select the "maximum aperture" of f/5.6, the diaphragm closes a bit, so the real maximum aperture with diaphragm fully open is some unknown value greater than f/5.6. Is this normal for this lens, or is my copy defective in its apertures? What I mean is, that maybe my diaphragm is misadjusted and f/5.6 should have the diaphragm fully open.

Thanks!

It can go further open because the maximum aperture size of the shutter is bigger than the lens needs. A 90mm f/5.6 is still in a Copal #0, for instance, which needs a wider opening to reach f/5.6. I don't think any lens has an arbitrary "stop" to prevent the blades opening up further.

As for closing ever so slightly in to get to f/5.6, I'll have to check mine when I get home. I've never noticed that, but I've never looked specifically either.

Perfectly normal for aperture selector to go beyond f/5.6 and f/32.

If you see the blades begin appearing ever so slightly at f/5.6, your lens very likely still falls well within acceptable standards.

BTW, I've heard of other Schneiders in the XL family doing this (Copals 0 and 1) and it's a negligible issue.

I have a 47XL that does this too. The lens isn't really "faster" than 5.6, despite what it might look like from the aperture lever indication, due to the way the image cone forms in that area, I believe.

Both my 110XL and 80XL allow for the aperture selector to go beyond the aperture scale, however the aperture blades are not visible from the front element of the lens when set to the maximum aperture on the scale, f/4.5 in the 80XL and f/5.6 in the 110XL, but they do appear in the first 1/3rd of stop after that. I guess I will measure the shutter speed accuracy and then test across all apertures with one roll of slide film, since my building is a nice zone 6 gray. I am 2 days in the 2 week evaluation period of KEH.

Just looked at mine and I can see the barest hint of the blades peeking in at the f/5.6 setting. Unless it's grossly off I'm sure it's okay.

I got the test slides back, and I can confirm that all the exposures are right on. I tested at various apertures from minimum to maximum with and without the IIIB center filter. So the lens is could actually be a bit faster than 5.6, but I do not know how much, because at 5.6 the diaphragm blades are quite visible.