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Possible Problem with Enlarger Lens?

thefizz

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I have a very good 90mm Computar lens for about 15 years but recently noticed a ring of something forming on the base (see image) of the lens. Should I be concerned? Maybe it’s always been there and I never noticed.
 

koraks

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I can't quite tell from the picture, but is the whatever-it-is forming along the edge of one of the lens elements? If so, it looks like a rather strong case of Schneideritis. In this case, it would be harmless.
If it's actually in the optical path, it looks more like separation of lens elements within a group, and that would pretty much mean the end of the lens.

So it really depends on where this is happening, exactly.
 
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thefizz

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Unfortunaly it looks like it's on one of the internal elements.
 

koraks

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Oh, that's a bummer...well, when stopped down, the problem is likely unnoticeable anyway, so maybe just keep an eye on it and just continue enjoying the lens.
 

ic-racer

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Agree with above that it is hard to tell as the construction of the lens is said to be 6/4, so two glued surfaces, probably one on each side of the aperture.

However, from the angle of the photograph, the abnormality does not appear to be in the light path. So I'll say it is deterioration of the edge paint.
 

Patrick Robert James

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The cement Computar used to cement the elements together pretty much always fails. I've recemented half a dozen by now. It is a shame because they are fantastic lenses, especially the 65 and the 135. I've never used the 90 but if you like it you could have it recemented. On the plus side, the elements come apart easily with just a soak in acetone. I am not sure what the refractive index is on the cement they used but I've used Canada Balsam to recement them and it has worked out fine. Of course the cost of fixing it would most likely exceed what it would cost to get another lens unless you do it yourself.
 

xkaes

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I agree that it looks like the start of lens separation, but it might not get any worse. In my opinion, it's irrelevant, because you never use your lens wide open -- except when focusing, when it's also irrelevant.
 

Hilo

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I had some Computar lenses that came with a similar issues, except the problem spots were yellow-brownish and had a more smooth structure. I gave them back to the seller. Now, I only use their 65mm.

These problems were so unfortunate for this company that really tried to take enlarging lens designs to another level.
 

mshchem

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I would still bet it's simply "Schneideritis" the black paint applied to the edges of the assembled elements come loose and create this terrible appearance. I wouldn't fool with the lens unless it drives you mad. I print 2 stops down from wide open for most everything. I admit that I avoid lenses that look like this.
 
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thefizz

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I made a print today with this lens and then another print from same neg with my 105mm Nikkor and they were very similar, so it’s not a problem as yet.
 

ic-racer

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thefizz said:
I made a print today with this lens and then another print from same neg with my 105mm Nikkor and they were very similar, so it’s not a problem as yet.
Click to expand...

Yes, the abnormality is not in the light path. Again, probably deterioration of the paint on the edge of the lens.

 

DREW WILEY

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It's "Schneideritis" as others have noted - a non-issue. Just ignore it.
 
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