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View Full Version : Super Angulon 90mm f8 fstop scale off kilter



rachjak
21-Dec-2017, 12:38
Newbie here, acting on LF photography fantasies stimulated by the images of Thomas Struth. Bought a used (I guess they're all used at this point) SA 90mm f8 for my Sinar F1 in a McDonald's parking lot and didn't notice until I got it home that the pointer on the fstop scale goes well beyond the end of the scale (beyond f8) when the lens aperture is all the way open. Pushing it back to f8, I notice the aperture is slightly narrower than the lens pupil - partially stopped down, in other words. Do I need to find a way to recalibrate the scale? The action in the aperture is smooth, slow shutter speeds test well, glass is nice and clean, etc. I appreciate any feedback.

ic-racer
21-Dec-2017, 12:48
Copal aperture scales sometimes have a number. Does yours?
173012

Louis Pacilla
21-Dec-2017, 12:52
A picture of the lens would help but my hunch tells me the 90 SA f8 scale is just as it should be and your just suffering from the nervous newbie syndrome.

rachjak
21-Dec-2017, 13:08
A picture of the lens would help but my hunch tells me the 90 SA f8 scale is just as it should be and your just suffering from the nervous newbie syndrome.
No doubt I'm nervous - this ain't a cheap hobby I'm finding out. In this case I think my anxiety stems from the fact that lens seems to be partially covered by aperture elements at f8 which, on an f8 lens, would presumably mean the lens should be wide open. No?

adelorenzo
21-Dec-2017, 13:18
I'll try to remember to check mine when I get home tonight but IIRC it works the same. I wouldn't worry about it.

Steve Goldstein
21-Dec-2017, 13:39
Once upon a time I sent a shutter for CLA and when it returned to me it had the same problem. I noticed that the ring that controlled the turning was held on by two tiny screws from the rear. On a hunch I removed the screws, rotated the ring 180 degrees, and put the screws back in. That fixed it. Apparently that ring was removed during the CLA and was reinstalled incorrectly.

Those tiny screws have tiny threads and require very little torque to tighten.

rachjak
21-Dec-2017, 17:03
Copal aperture scales sometimes have a number. Does yours?
173012
No number.

Keith Pitman
21-Dec-2017, 17:09
My SA 90mm, f/8 does the same as do other lenses. Nothing to worry about. Try it with film.

rachjak
21-Dec-2017, 17:11
173044

Scale pointer at far right in photo, well beyond f8. This where the aperature is wide open. Moving it back to f8 stops the lens down slightly. Thanks a lot for the input.

rachjak
21-Dec-2017, 17:12
Pointer at far right.

Jim Jones
21-Dec-2017, 18:21
Shutters are manufactured to accommodate different lenses. Most 90mm f/8 lenses don't require as large a maximum aperture as these shutters. There's no real need to block the shutter from opening more than enough for whatever lens is installed in the shutter. You can easily check the aperture scale by measuring the apparent diameter of the aperture opening as seen through the front lens cell. Don't get your eye really close to the lens while doing this to avoid a parallax error. The apparent diameter of the aperture should be 11.25mm at f/8. An error of a millimeter or so will cause little exposure error.

rachjak
29-Dec-2017, 12:07
Thanks, Jim. I measured the apparent diameter of the pentagon - from one long point to it's opposite side - and it's right on the money for 90/8. Thanks a lot for your suggestion.

xkaes
29-Dec-2017, 12:15
173044

Scale pointer at far right in photo, well beyond f8. This where the aperature is wide open. Moving it back to f8 stops the lens down slightly. Thanks a lot for the input.

The pointer looks slightly bent to me.

ic-racer
29-Dec-2017, 17:05
Other than the little bend that was observed by xkaes, the aperture scale looks the same as other correct 90/8 examples I have seen or used.
Here is an example of obviously incorrect scale for that lens:

173164