Scratches?

[Casey]

I've just purchased a gorgeous 210mm lens that happens to have two small, superficial scratches on the rear element, about halfway beteen the rim of the glass and the center of the glass. They're small enough to where I didn't notice them the first two times I examined the rear glass. How much of a factor are these scratches going to play in terms of negative quality, and subsequently print quality? I shoot both color and B+W.

Thanks,

Casey

[Jack Flesher]

If you hardly noticed them on initial inspection, I doubt they will impair image quality to any significant degree. However, scratches on the rear element are more serious than similar marks on the front element. You would most likely notice any deleterious effects when shooting into a bright light source and these would be in the form of flare or streaking around the sratches.

[Capocheny]

Hi Casey,

I'd suggest you go out and take some pictures with the lens to ascertain whether or not the small scratch has any impact on the image.

That's easier than all the speculating we can do since we don't have your lens in hand.

But, it "probably" won't have much impact. :)

Cheers

[Donald Qualls]

The worst effect likely from scratches at minor as you describe is just loss of contrast when against the light; if that is a problem, you might be able to fill in the scratches with black ink to reduce the effect. Typically, however, as suggested above, if the scratches weren't obvious immediately, they probably won't have any detectable effect on your images.

[JW Dewdney]

... you might be able to fill in the scratches with black ink to reduce the effect.


I would imagine a proper job filling them with india ink would absoulutely and completely eradicate any nasty effects on the image, wouldn't you think? Perhaps - apart from being 1/500th of a stop dimmer than the indicated aperture...?

[Jim Jones]

I would imagine a proper job filling them with india ink would absoulutely and completely eradicate any nasty effects on the image, wouldn't you think? Perhaps - apart from being 1/500th of a stop dimmer than the indicated aperture...?

Theoretically there should also be a slight loss of sharpness due to diffraction. I doubt if it will be noticable.

[E. von Hoegh]

Hi, Casey.

Here is some anecdotal evidence. A few years ago, I found a pre WW1 9.5" Dagor at a camera show. It has a deep scratch near the center of the rear element. I purchased it for the shutter, $45. I thought I would put my other barrel Dagor in the shutter.
Well, I blacked the scratch with India ink, tried the lens, and it works just fine!

I have compared it with my 240 Berlin barrel Dagor, and can see no difference.

[erie patsellis]

Interestingly, I just purchased these: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=29986&item=300020239121

figuring I can use the compur #1 for a 240 G-claron. I blacked out the nasty looking chip in the front and mounted it on my 4x5. I'll be damned if I can see any effect from it the ground glass whatsoever. As an added bonus, I put the lens on my 8x10 and suprise of all surprises, it illuminates well past the ground glass (with some softening and slight falloff in the corners). Hopefully I'll get a few sheets of 8x10 shot and processed this week, with any luck, I"ve found myself a new wide for my 8x10.


erie

[Casey]

Thanks for all the input. The lens is a Rodenstock Sironar N MC. I'll go shoot a few photos of bright objects, then determine whether or not I should fill the scratches with india ink. The proof is in the negatives.

Thanks again!