Lens Decementing Problem

[nick_morris]

Hello, I just received a lens I bought on eBay. I was surprised and

pleased to find it was a "Production Standard Quality Control" lens,

but found that it has what may be a serious problem. It looks as if

you are looking into an eye when you look into the front component of

the lens with the shutter closed. There is a dark circle about a 1/2"

in diameter just off center, surrounded by a lighter, mis-shapen

circle. When looking through the lens, into the light, with the

shutter open, these circles are faint, but visible. They appear to be

below the surface of the glass. Several people I've discussed this

with (they haven't seen the lens) have suggested that it may be that

the elements have de-cemented. The lens is a 13" Wollensak Series 1A

Raptar for my 8x10, which has 4 elements in the front component. It

appears that this de-cementing, if that is the problem, may have

affected two of the elements in the group. I have put the lens on the

camera, and the image on the GG looked good, but I have been told the

problem may transfer to the film. Of course, the best way to know if

and to what extent the problem will manifest on the film is to test,

which I will do. However, I am interested to know if anyone has had

this type of situation? Did it have an affect on picture quality? Is

it a condition that gets worse? Any information would be helpful. I'm

not particulary afraid of less than pristine lenses. I have had some

very good results with some pretty crappy lenses, but those results

can not always be relied on with a bad lens. Again, any information

and experience shared is appreciated. Thank you.

[conrad_hoffman]

Could be coming unglued, or it could be a fracture. Go to the S.K. Grimes site and see if they still have all their info on re-cementing lenses. IMHO, when the elements separate badly, it's not a good thing and needs to be fixed.

[User_503771]

Sure sounds like de-cementing to me too. I've only encountered this a few times and the look of it stays with you, it's a fairly unique-looking phenomenon.

 

Probably the most important factor is whether or not the elements have shifted at all while coming unglued. Seems almost impossible that they wouldn't have, but I'm not a big expert so I certainly can't say.

 

You're absolutely right to test the lens before making any big decisions about the thing. Could be that the worst thing that would happen would be a very slight increase in flare, which would be easily countered with a lens shade. In my early days using large format I used some pretty crappy lenses and got surprisingly good shots with them (still wish I had some of those lenses!) so the "proof is in the pudding". I've read various literature from 50 to 100 years ago that talks about various lens faults and how to deal with them, and it's surprising how much damage a lens can take before it really affects image quality. I've read that even a full fracture in a lens element doesn't necessarily mean the lens is unusable -- it'll just give more flare!

 

If you decide to have it re-cemented, I'd shop around and get some quotes. This can run a pretty penny and Grimes isn't the only fish in the sea. You might find a place that already has the "template" set up for the Raptar, and that alone could save quite a bundle.

 

If I recall correctly, there's a place in Arizona or New Mexico, can't remember which, called (maybe) Focal Point(?). They do this work. There are also various firms overseas you could check out.

 

I'd be very curious to know how your tests come out. Will you be comparing this lens with any other one? Do let us know the results!

[nick_morris]

Thanks for the responses. I have spoken with John of Focal Point, Inc. in Colorado. He said it sounded like lens decementing, but for the definitive answer, he would have to see it. This lens has four elements in the front (also the rear) group. It would be relatively expensive to repair, and the repair effort can be risky.

I developed three sheets film shot with the lens, and one showed what appears to be siginificant flair wiping out a portion of the scene, but the other two looked good. I haven't had a lot experience with problem situations, and I have had a similar flair problem with good lenses, so I'm not sure if I identified a problem with the lens, the holder or my technique. The two that turned out good were shot at relatively wide apertures (8 1/2 and 11 1/12). I have several other sheets to process, and I'm showing the lens to an experienced professional photographer Wednesday. I'm afraid I pushing this too hard, but it is such a nice lens in every other respect. I have an older, uncoated sample of this lens, which has a chip on the edge of the rear glass of the front group. I put varnish in the chip, and this has been a fine lens in use, comparable to the Dagors I have.

[nick_morris]

I thank you all for your help. I spoke with John at Focal Point. He said it sounded like decementing, but that he would have to see it. Being that the front group, which has the problem, is comprised of four elements, the cost of the repair will likely be over $300, plus shipping.

I shot with the lens, and the results were very, very good. At first, on one shot I thought I had serious flair, but after looking at the negative a little longer I realized that the behind-the-lens filter frame slipped into the path of the image. A long story, but certainly a "problem" that can be corrected. I made negatives at apertures of 8 1/2, 11 1/2, 32 1/2, and 45; and all looked good. Excellent shadow detail, and very sharp. Results were superior to negatives made with my 9 1/2" Dagor, which is a very good lens.

I plan to keep the lens. At what point I have it repaired, I don't know. I guess I'll keeping shooting with it until it shows a problem on the film.