aperture markings on 450mm, extend them?

[Daniel_Buck]

I've just picked up a fujinon 450mm, and I notice that the aperture closes down quite a bit more than the scale goes, the scale goes to f64, and it looks like the aperture closes down another 3 stops or so.

It looks like the aperture marks are in very even liner intervals, could I assume that the next 3 stops would follow the even intervals, no space difference between them? f90, f128, and then f180 I assume?

I don't expect to use more than f64, but since there's more room, I figure I might as well mark them. Is there a reason these were not marked? Is it just assumed that nobody will ever be stopping down passed f64, even though the aperture actually goes another 3 stops or so? I guess this is because it's in a small shutter (#1) that's meant for shorter lenses, so the physical size of the opening isn't very large?

[W K Longcor]

It has been a good number of years since I was studying optics in my photography classes -- but I seems to me that at a certain point, the tiny aperatures cause a problem with defraction -- that makes for fuzzy images. It is a bit like a pin-hole camera ( even though there is a lens involved) where everything is in focus D O F wise -- but nothing is really SHARP. So lens designers limit how small a usable aperature is available. This isn't saying you can't use that smaller aperature. How the lens stops down is a mechannical situation, it MAY be lineal in the amount of stop down or it may not. If you really want to use the tiny aperatures, the best bet would be to expose some film and see what works. Maybe someone out there has been at the books more recently that I have -- and can add to -- or correct this, if my memory is faulty.:)

[bsimison]

Have you shot with the lens yet? A couple of years back, I picked up a used Schneider 150mm Symmar-S with the same issue. Turned out someone had traded the Copal shutter out and had neglected to correct the aperture scale for the 150mm lens.

Here's the thread regarding that lens. (http://www.largeformatphotography.info/forum/showthread.php?t=21689)