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Opinion needed: optical issues with two of my Bronica lenses


antonio_piu

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Two of my lenses (one from my GS-1 system and on from my ETRSi system) show some issues in the glass, I'm providing a couple of pictures below.

 

The PG 50mm shows something that looks like little dots or droplets, it would look like condensation, but it certainly isn't.

The PE 100mm has a circular smudge, like an abrasion or discoloration.

 

Both issues are only visible under direct light, and if I'm not looking straight into the lens, but rather tilting them on a side.

What do you think those are? In particular, I wonder if the abrasion on the external circle of the PE 100mm might have consequences in the final image.

 

Any help or advice is highly appreciated. Thank you.

 

zenzanon-50mm-1.thumb.jpg.17e8226654e27dc3398fc68b617fbf56.jpg zenzanon-50mm-2.thumb.jpg.8d9537e42242cf595c32a9bc9b2e2710.jpg zenzanon-100-1.thumb.jpg.730cc1567ea13f12803123ab49fa300f.jpg zenzanon-100-2.thumb.jpeg.b5b42cae73f313ecf97bfcbe4a266513.jpeg

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I'm guessing that could be the beginnings of fungus (spots) and separation (edge).

 

Thanks Conrad – I've only shot the one with potential separation as an adapted lens on my Canon 6D, so I have no way to judge whether it affects the image when used on my ETRSi.

 

Do you think the beginning of separation on that peripheral point is likely to affect the final image on the 645 format?

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I used to have an old Miranda 35mm screw-mount lens with some edge separation in the rear element group, and it did not visibly affect images. I have another lens with small bubbles in between two elements (similar to what your photo shows), and likewise it isn't an issue. If it was severe separation (e.g., due to impact) then it would be more of a concern.
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Thanks John, that's nice to hear.

 

I have another lens with small bubbles in between two elements (similar to what your photo shows), and likewise it isn't an issue.

 

So, you think that also is a separation problem? Because that's another lens, it's not the same that shows the clearly defined arc shaped defect.

 

These are two different lenses. I should have done a better job when posting. But here is a quick remark: first two pictures are about Zenzanon PG 50mm (shows pattern like droplets) - last two pictures are a Zenzanon PE 100mm (shows a discolored arc).

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So, you think that also is a separation problem?

 

It's hard to say from your photos, but it could be. Here is a photo of my lens with the little droplet-like bubbles, which I believe is due to separation.

 

IMG_9250.JPG.a30cc17185cbad4c41d09ed138511111.JPG

 

Enough spots or slight edge separation (like haze) could reduce contrast slightly due to light scattering, but I don't think it's anything to be concerned about.

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I'm with the school that sees Piu's problems as possibly the first stages of fungal growth.

 

What's showing, in any case, is unlikely to have any serious effect on mage quality until it gets a lot worse. If it is fungus, and if it can be killed by UV or some such, not to worry.

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The first shot appears to show fungus contamination, and the 3rd and 4th are almost certainly the beginning of cement separation.

 

Fungus, in its early stages, can usually be fairly easily cleaned away after dismantling, but cement separation generally can't be economically cured. However, as John says, the separation has to be pretty bad before it shows in the image.

I have a 180mm Rodenstock (infamous for separation issues) Siranon LF lens that has separation across about 1/3rd of the lens surface - and it's still the sharpest lens I have for 5x4! There's a pretty rainbow patterning to look at as well. :rolleyes:

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