what causes this lens problem?

asp.artist · Apr 17, 2010

Hi, I've been getting these light spots in the center of the image while using a 90mm lens. The lens looks clear and the mechanics work well. The camera is an Agfa Ambi silette. 90mm lens with shade and medium yellow filter. 2 different rolls of film. Images shot with the 50mm are fine.

Any idea what caused this?

BobD · Apr 17, 2010

I have the same camera and lenses. I can only guess it's the filter but you
didn't say if you used the same filter on the 50mm lens.

Is it a vintage filter?

asp.artist · Apr 17, 2010

It's a vintage filter. And that day I was using 2 bodies, one with the 50 and one with the 90, and separate filters on each.
If a filter looks clear will it still affect the image?

glbeas · Apr 17, 2010

Looks like internal reflections, as if there were a fine layer of fungus or oil on the inner surfaces.

underground · Apr 18, 2010

glbeas said:
Looks like internal reflections, as if there were a fine layer of fungus or oil on the inner surfaces.

I agree. Same lens same problem on two different bodies.
It should be able to be Identified if you open up your
lens and look threw it at a bright light source and spin the
forward end slowly in a figure eight motion.

you should see a problem if there is one.

Long shot, but if your lens coating is worn bad in the center of your element.......

asp.artist · Apr 18, 2010

I tried your suggestion about looking through the lens at a light. It looks pretty good. Might be a small "smudge" type mark in there. And the filters look fine, too. The filter size is 35.5, or 37 push-on, and I've been unable to find these new. So, I'll take it out again today, and try again.
Thanks for your suggestions.
Anne

Rol_Lei Nut · Apr 18, 2010

The degree of the problem looks like it could be within the "normal" behaviour of a flare-prone lens.
Different lenses also interact differently with filters, so maybe without the filter the problem will be reduced (however well it behaves with the 50mm).

canuhead · Apr 18, 2010

could you post a larger version of the photos, it'd be easier to see the problem,thanks.

asp.artist · Apr 18, 2010

Here are more images. It was a bright day at about 4 -5 Pm. So the sun going down was starting to be a factor (sunset is 7:30pm). The third shot the sun would not have been a factor. (Just a bad photo.)

canuhead · Apr 18, 2010

thanks, much better. first blush would be flare but wouldn't rule out lens issue either. don't suppose you have a shot looking through the lens do you have you tried with and without the filter as well ?

asp.artist · Apr 18, 2010

The weather has not cooperated. I'll try it with out the filter when the sun comes back out.

Thank you very much for your help. I never knew flare could look like this. Or that a filter could be such a factor.
Anne

what causes this lens problem?

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