Aperture indicator not aligned

[cablerelease]

I have a Fujinon W 125mm F/5.6 lens that I recently got from a seller on eBay. It's in great condition, however, the little indicator to show the aperture setting doesn't appear to line up when you have it wide open to f5.6. When you rotate the aperture lever to get to 5.6 you can see the lens close down slightly. You can see the actual lens and where the indicator is on the listing here.

Does this mean that the lens is a little faster than f5.6 and I can expect that the exposure is accurate when the indicator shows 5.6 and other subsequent apertures?

Or does this mean that there is something off and I will not be able to expect accurate exposure settings as indicated?

Lastly, if this means the lens is off or messed up in any way is this repairable?

Are there any tests I can run to evaluate if the exposures are accurate or not (while minimizing burning through a lot of film on the tests?)

[Bob Salomon]

Sounds normal.
Shutters don’t know what lens will be on it. That’s why aperture scales are screwed onto shutter while shutter speeds aren’t. It isn’t at all unusual for the aperture to open slightly more. But it won’t make your lens any faster.

[cablerelease]

Sounds normal.
But it won’t make your lens any faster.

If this is true then how do I know I'm setting my lens to an accurate exposure?

When I slide the aperture lever to the first notch (f5.6) on the scale I can see the lens close down slightly. Or is what you are saying that when the indicator hits f5.6 on the scale I should expect that to be accurate to f5.6 while ignoring the fact that the lens might be opening up a bit wider beyond the scale?

[Dan Fromm]

Mine's like that too. All OK. Trust the indicator.

[Bob Salomon]

If this is true then how do I know I'm setting my lens to an accurate exposure?

When I slide the aperture lever to the first notch (f5.6) on the scale I can see the lens close down slightly. Or is what you are saying that when the indicator hits f5.6 on the scale I should expect that to be accurate to f5.6 while ignoring the fact that the lens might be opening up a bit wider beyond the scale?

You can be sure it’s accurate unless someone remounted the lens cells into another shutter. Then the scales would be wrong if that shutter had scales from a different focal length lens.
If you look closely at your scales you will see that the have a small number on the left end. The 5.6 scale for a 90mm in a 0 shutter is different then the ones on a 150mm lens.
If you want to make sure expose some film. Otherwise take a meter reading through your gg with a meter with a gg or microscope adapter on it. If you do this just remember that your gg and fresnel absorb light so you have to determine how much light loss they have and use that as a filter factor.
If you don’t have a meter that can do this then shoot some film.

[cablerelease]

Mine's like that too. All OK. Trust the indicator.

Ok good to know. Thanks.

[cablerelease]

You can be sure it’s accurate unless someone remounted the lens cells into another shutter. Then the scales would be wrong if that shutter had scales from a different focal length lens.
If you look closely at your scales you will see that the have a small number on the left end. The 5.6 scale for a 90mm in a 0 shutter is different then the ones on a 150mm lens.
If you want to make sure expose some film. Otherwise take a meter reading through your gg with a meter with a gg or microscope adapter on it. If you do this just remember that your gg and fresnel absorb light so you have to determine how much light loss they have and use that as a filter factor.
If you don’t have a meter that can do this then shoot some film.

Thanks Bob.

[mmerig]

Another simple test is to compare exposure readings through the ground glass using two different lenses (assuming you have another besides the one you just bought). Use a uniform target, like a wall, that extends beyond the field of view for both lenses, and take the reading at or near the gg center. Use a few f-stops that both lenses have in common.

I would be suspicious about a lens iris that does not open up enough to allow the whole lens to be used at maximum f-stop. I have bought used lenses that had this sort of mis-match, and when I did the above test (plus measuring entrance pupil), a full-opening iris was correct.

[Chauncey Walden]

You could call it a feature that automatically adjusts the exposure by stopping down a bit to compensate for the shutter actually being slower than marked;-)

[Dan Fromm]

I would be suspicious about a lens iris that does not open up enough to allow the whole lens to be used at maximum f-stop. I have bought used lenses that had this sort of mis-match, and when I did the above test (plus measuring entrance pupil), a full-opening iris was correct.

Mike, I can't speak for the OP's lens and shutter but mine's diaphragm opens fully. When fully open the aperture indicator is slightly to the "larger aperture" side of "5.6". The diaphragm is, however visible through the lens when the indicator is at 5.6. Ever so slightly stopped down, not worth worry.