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Photo Forum / Digital Photography / DSLR Cameras / April 2006marks on back glass of lens a problem?
I'm looking at a used lens described as having 'marks on back glass' but I think this is where it would be a big problem, right? A little scratch on the front is no big deal but the back? > I'm looking at a used lens described as having 'marks on back glass' but > I think this is where it would be a big problem, right? A little scratch > on the front is no big deal but the back? <self absorbed mode> I thought this post was going to be about me. </self absorbed mode>  SignatureMark Mostly photography... http://www.marklauter.com Ha! >>I'm looking at a used lens described as having 'marks on back glass' but >>I think this is where it would be a big problem, right? A little scratch [quoted text clipped - 3 lines] > I thought this post was going to be about me. > </self absorbed mode> It's funny but the sharpest lens I have ever had on a camera (Leitz DR Summicron 50 f2) had fungus marks on the rear element, so I bought it for $100. I hardly ever use 50's so I sold it to a friend who is still using the lens and loves it. But after that I bought a Leitz Elmarit 90mm f2.8 with a bad scratch on the front element, wasted my $ the flare from the scratch killed the image quality. If I was buying a damaged lens I'd ask to take a few frames first, certainly don't buy one with a no return policy. Tom > It's funny but the sharpest lens I have ever had on a camera (Leitz DR > Summicron 50 f2) had fungus marks on the rear element, so I bought it [quoted text clipped - 4 lines] > damaged lens I'd ask to take a few frames first, certainly don't buy > one with a no return policy. Well somebody just bought a nikkor 17-35mm f/2.8 for $620 I'm such a wimp on ebay, it gives me an ulcer, I should stop even looking <g>. It was also somewhat mislabelled. >> It's funny but the sharpest lens I have ever had on a camera (Leitz DR >> Summicron 50 f2) had fungus marks on the rear element, so I bought it [quoted text clipped - 10 lines] > > It was also somewhat mislabelled. Whenever I sell something on eBay I always take detailed photos of any problems. I don't know what a "mark" is without seeing it. The mark may be a problem, it may not. Like the other poster, I had a Hassleblad with lenses where the elements were separating and you could see the glue around the edges. Still took incredible photos, however. Ask questions and ask for more photos if they are not clear. Furthermore, I've found that many sought after lenses sold on eBay often go for around the same price as the same lens brand new, so be sure to do your homework before placing a bid. > Whenever I sell something on eBay I always take detailed photos of any > problems. I don't know what a "mark" is without seeing it. The mark may be [quoted text clipped - 6 lines] > the same price as the same lens brand new, so be sure to do your homework > before placing a bid. I just noticed it a couple hours before closing. Damn a $1700 lens for $620 though. It could well have been bought on ebay by the seller for $300 because the damage is bad and this seller made a killing so I guess I don't mind missing it. I agree the normal sales are overpriced on ebay. It takes a lot of patience and study to actually get a good deal. Not worth the ulcers. Besides that lens is too big & clunky. Ha! $620 is still a chuck of money, for a 17-35 2.8 wew it is a good price. I just bought 2 lenses on Ebay for my D200, one was a 24 f2 that was going for $3-400 on Ebay and the usual used sources and I got it from a non photo provider for around $200 perfect condition. Probably the non photo seller was the key here, the lens is going for $800+ new. The other lens was a 70-210mm f4, these had been going for $250 or so on Ebay, I lucked out and got this one for less than $200, nice glass, few scuffs. Here it had a filter on the front, first tried it with the filter, fairly soft, took the filter off, this was a sharp lens, I have seen filters degrade images but never to the extent of this lens. Again I only paid in the $200 range for each of these lenses, if I had a spare $600 i might have gone for that 17-35. There are some deals on Ebay, you just need a little luck and some good research. Good luck Tom > It's funny but the sharpest lens I have ever had on a camera (Leitz DR > Summicron 50 f2) had fungus marks on the rear element, so I bought it [quoted text clipped - 4 lines] > damaged lens I'd ask to take a few frames first, certainly don't buy > one with a no return policy. Generally marks on the rear elements *do* have more effect. If depends of course on what kind and how bad of a mark... A deep scratch (or scratches) can be filled with black enamel (paint), reducing it's effect to unseable/unmeasurable. The only difference is an insignificant loss of light transmission due to the blacked-out area (maybe 2-3%). >A deep scratch (or scratches) can be filled with black enamel (paint), >reducing it's effect to unseable/unmeasurable. The only difference is an >insignificant loss of light transmission due to the blacked-out area >(maybe 2-3%). What about bokeh? Won't the shape of an out-of-focus point of light change? Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>A deep scratch (or scratches) can be filled with black enamel (paint), >>reducing it's effect to unseable/unmeasurable. The only difference is an [quoted text clipped - 3 lines] >What about bokeh? Won't the shape of an out-of-focus point of light >change? Same 2-3%. SignatureFloyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com > But after that I bought a Leitz Elmarit > 90mm f2.8 with a bad scratch on the front element, wasted my $ the > flare from the scratch killed the image quality. You might well be able to reduce the effect by filling the scratch with something with a higher refractive index than air and buffing it up. for example see http://www.watchpolishing.com/antiscratch.htm > Tom > "tomm42" <tmonego@wildblue.net> wrote in message >>But after that I bought a Leitz Elmarit >>90mm f2.8 with a bad scratch on the front element.. > You might well be able to reduce the effect by filling the scratch with > something with a higher refractive index than air and buffing it up. > for example see > http://www.watchpolishing.com/antiscratch.htm >>Tom Even better, IMO, would be to paint over the scratch with flat black paint and a fine brush. Yea, it will look ugly as heck.... -Greg >> "tomm42" <tmonego@wildblue.net> wrote in message > [quoted text clipped - 10 lines] > Even better, IMO, would be to paint over the scratch with flat black > paint and a fine brush. Yea, it will look ugly as heck.... That's the standard approach with astronomical glass I understand. Even had to do it at Palomar a while back after some twit with a .22 managed to take some potshots at the mirror. Seems that he didn't quite grasp that a 20 ton Pyrex astronomical mirror isn't quite as fragile as the one in the bathroom. Personally I think they should have put him at the prime focus and pointed it at the sun for a while. > -Greg Signature--John to email, dial "usenet" and validate (was jclarke at eye bee em dot net) |
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