aperture problem

[back alley]

i just today noticed that my 28/3.5 lens does not stop all the way down.

it's supposed to go dowm to f22 but the actual opening does not change from 16 to 22. in fact the ring does not actually ever hit 22, almost but not quite.

is this a case for the experts to repair or is there something i can do?

joe

 

[ray_g]

I would only bother if you would shoot it at f/22.

 

[Sonnar Brian]

Are you sure that the aperture ring is well calibrated? Is it all the way open at F3.5, or do you have to turn the ring slightly beyond F3.5 to get the blades to fully open?

I have a Nikkor like this, it will "slip" sometimes so that I have to go beyond F1.4 to open it up and it fully closes before reaching F16. I got it back into position then tightened it up.

When I had the 135mm F3.5 disassembled way beyond what I thought I could handle, I noticed some fine-tune set screws for adjusting the relative position of the aperture ring. Yours could be slightly off. The blades might be fully closing before the ring hits F22. That could be a problem for exposure.

 

[back alley]

Is it all the way open at F3.5, or do you have to turn the ring slightly beyond F3.5 to get the blades to fully open?

i do have to turn it a bit to have it open all the way.

so chances are that closed down at just past f16 but not at f22 it is closed all the way already?

joe

 

[Sonnar Brian]

That is what I think. These older lenses did not use a "linear" aperture, ie equidistant movement between F-Stops. The movement between F16 and F22 is tiny. That movement on the F3.5 side of things does not seem like much distance- maybe a mm or 2-, but imagine that much of a throw on the F22 side. Be careful when you stop it way down, you could be getting a ~1/2 stop exposure error, the difference between what the aperture blades are actually set to and where the aperture ring indicates. Note the setting of the ring where the blades stop closing down. That is "really" F22.

 

[back alley]

if i ever learn how to use a 28 well, i think i'll opt for one in better shape.

i have been looking this one over with a loupe tonight and i noticed what looks like a small scratch on one side of the front element and a teeny bit of possible fungi on the other edge.
the rear element has been cleaned a bit too much also.

there is an antique shop in australia that also sells old cameras & lenses that i will never deal with again.
joe

 

[Sonnar Brian]

Chances are those will not create any affect on the photo's. I have bought "mint" lenses with obvious flaws in them, no need for a loupe. And of course they were "as-Is, we are no experts". Live and learn, but it has cerianly slowed down my Ebay buying to "as-Is, CHEAP".

Time for bed, and no Ebay tonight!

 

[back alley]

no effects on pics so far that i have noticed.