Impact of cleaning marks

[m.bruehl]

Hi,

I did some searching, but found no really illuminating answer:

I just got an 8/165 SA, and was happy as can be - until I held it against the light. The surface of the front lens - that looked absolutely O.K. on first view - was sort of matte, sometimes a little blue or green colored. Upon closer inspection I saw, that the complete front lens showed microscratches in coincidal distribution. Depending on the viewing angle the surface seemed absolute normal or looked like a frozen sea after days of ice-skating.

You may call me picky, but I am afraid that this amount of "cleaning marks" has an impact on contrast and sharpness, even if I take photos using a shade/compendium to prevent direct light from the sides.

What do you think about it?

Regards

Michael

[walter23]

I have a schneider 150/265 with some light fog inside that is only visible under very specific lighting glancing the internal element just right. It seems to have lower contrast than my other lenses, but my others are also newer designs with better quality coatings so I'm not sure how much is a consequence of the fog. I'm pretty sure the fog is decreasing contrast a bit though. So far this has been more of a benefit than detriment to my photography with the lens

The only way you'll know is to test the lens for yourself. Put the lens through its paces, shoot in backlighting, etc, and see what happens.

[rob]

It could be scratches on the coating itself, not the glass. Some of my lenses and filters have a lot of "cleaning marks", but they perform just fine. May be my habit of using shade helps. I would say, try it first.

[Peter K]

Cleaning marks, also "only" in the coating, can ruin the performance of a lens. With a WA lens like the SA and it's 100° angle of view a shade won't help much. So as said before, test the lens and when contrast and sharpness suffers, ask at Schneider if the lens can be repaired.

[m.bruehl]

Thanks for your comments.

What setting would you propose to test on decrease of contrast/sharpness, if you don't have the same lens with perfect surface available?

I have a test-sheet, so I could take some 6x9 with my 90 mm, which also has a very curved front lens, but this is a new lens with coating. So if I see a difference, I don't know if it's due to the lens or the cleaning marks ...

Or do you think about taking an outdoor picture and just say "Hey, seems to be O.K. for me"?

Any help appreciated.

Michael

[Brian Vuillemenot]

I highly doubt that the cleaning marks will have any noticable effect on the performance of the lens. I have lenses that have sustained considerably worse damage than you describe (including taking a small chip out of the front element) with no visable difference in performance after the damage.

[Glenn Thoreson]

The short answer: Only you can tell if it will be acceptable. If some test shots look okay to you, it's good to go. If you can't make it perform, get rid of it.

[Dan Fromm]

Michael, cleaning marks' effects on the final image depend on the marks and on the lens. Just ask y'r 165/8 SA whether it shoots well enough for you. If it does, use it and be happy. If it doesn't, don't use it and be unhappy.

I give you this advice because I have three lenses whose front elements have the classic "cleaned with a scouring pad" look. Two of them -- 210/5.6 Saphir, 210/6.3 Prinz (= Commercial Congo) -- are still very usable. The third, an 80/2.8 Xenotar, is just horrible.

Good luck, have fun,

Dan

[Peter K]

Michael, the front lens of the SA is nearly flat. But this isn't the problem. Some cleaning marks are normaly no problem also. In any case, the Super-Angulon is a lens with good contrast. So it should be easy to check the performance of the lens with some outdoor pictures. Or you can use Toepler's Schlieren method: put an illuminated diaphragm near the rear focal point of the lens. A white LED will also do the job. In some meters distance the image of the diaphragm will be projected on a roud screen with the same dimensions of the image of the diaphragm or LED. Behind this screen the lens will be observed with a telescope. The clean parts of the lens are dark, but every scratch, buble and so on is bright.

[David A. Goldfarb]

I've had one lens where I thought the cleaning marks were bad enough to create a noticably diffuse image, and I returned it to the seller for a refund. As the others have suggested, the only way to know with any given lens is to test it. Try photographing a high contrast scene, like an indoor scene looking out a bright window, and look for flare.

Remember that the surface of the lens is far from the focal plane, so physical lens defects aren't going to be anywhere near in focus. They just tend to add to veiling flare, and often not significantly.