Testing effect of scratch on front of M-90mm

Shadrash

Steven Hertel
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Dec 1, 2005
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Hi All,

I just picked up a used Elmarit f2.8 90mm for my Hexar RF. It has a scratch on the front element, so I got it for a good price, and I have 14days to get my money back.

The scratch is not in the centre of the lens, about half way between the centre and edge, and is 1mm.

What would be the best way for me to test the effect this would have on my images? I would like to run it through it's paces so I can decide if it is worth keeping.

Shoot wide open towards the sun? Any suggestions would be appreciated.
 
The early Summicron 90/2 I bought recently from another member, here, for a good price actually has a couple of small chips out of the front lens element. My test was to shoot with it, the sort of shots I'm likely to use it for. Of course it passed with flying colours! No sense condemning a lens because it can't pass a "worst case" test when in fact I'll never use it that way, and it works well in all normal situations.

Try it for normal shots, at all apertures. Do you normally shoot into the sun? Then try that too.
 
The effect of a scratch (1mm) on the FRONT element will have just as no effect on the picture. Indeed if you think you can prove it you must prove it wite open an in backlite situations. But even then I think the effect is nihil or just nothing.
 
If it's 1mm... it won't have any effect on your stuff. However, do as Chris recommended above (just don't burn your shutter curtains aiming at the sun!) and then have a photo enlarged to, say, 8X10.

You still won't find a thing.
 
How can you?

How can you?

The only way to test is to get two of the same, one with scratch, one without, and photograph identical scenes identically, on a tripod, to see if there's any difference. Even then, it's not a conclusive test.

Apart from that, what you can do is shoot the hell out of it over 14 days, see if the pictures meet your expectation in terms of contrast, flare resistance, etc. and decide if you think it's worth keeping on the basis of those pictures.

One tip from Kbcamera-- most PJ's lenses are scratched, by the very nature of their work (war, natural disasters, etc). Yet, their photos are still beautiful and memorable. So perhaps you do not need to worry so much about the scratches.

Wai Leong
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Shadrash said:
Hi All,

I just picked up a used Elmarit f2.8 90mm for my Hexar RF. It has a scratch on the front element, so I got it for a good price, and I have 14days to get my money back.

The scratch is not in the centre of the lens, about half way between the centre and edge, and is 1mm.

What would be the best way for me to test the effect this would have on my images? I would like to run it through it's paces so I can decide if it is worth keeping.

Shoot wide open towards the sun? Any suggestions would be appreciated.
 
Read the article on KB camera

Read the article on KB camera

It makes sense. I will put many rolls through it in real world situations, and see how it goes. Thanks for taking the time to answer.
 
My Nikkor 85/2 and Canon 35/1.8 look like they've been used to get personal with a sandstorm. For my stuff, it matters not at all. Of course, I'm not much for shooting outside.
 
No one can say for certain what the effect of the scratch will be. As mentioned, it appears that scratches on the front element have less effect on overall photo quality than scratches on the rear element. However, the scratch cannot be said to have 'no effect'. Of course it has an effect. The question is how detectable it is, and how much it bothers you.

I suspect that you won't see any difference, even if you had two otherwise identical lenses to test, in a print. If you scan your negatives with a reasonably high definition scanner, such as the SD IV on up, you MAY be able to detect the effects at 1:1 viewing after a high-resolution scan. However, I agree with the others that I tend to doubt you'll see it.

In my experience, problems of this sort tend to manifest themselves as an overall slight lowering of contrast, or very minor flare problems - of the sort you'd otherwise expect if you didn't use a lens hood, or had a dirty / scratched filter on the lens, etc. And again, I doubt you'll be able to actually detect it - but that is not the same as saying it is not there.

There is a fellow on PNET who posted some scans of photos he took with a lens that looked like it had been dug out of a cesspool and then kicked about by footballers for a year or so. The photos were fine, quality more than acceptable for web-posting. How much difference there would be between that lens and the same lens in undamaged condition, I could not say. It is possible that he'd never be able to do a huge enlargement with the 'bad' lens, whereas he could with an undamaged one - but as someone else here said, are you likely to be doing that?

And of course, one must consider the effect of owning such a lens on the owner. I'm not joking. I know some folks who are inveterate glass-peepers. They have their bright lights and their high-powered loupes, and they peer intently into their Nikon or Leica (just picking, sorry folks, but it does seem to be mostly you guys) glass and if they see ONE SPECK of dust, it's off to DAG or the equivalent. If they bought it off eBoy, God help the seller.

I'm not putting those people down. If that's you, then well and good - but you might want to think about how owning a lens flawed in this way is going to bother you sleeping at night, even presuming that you're satisfied that you can't see the difference in your prints or scans. Everyone has their lower limit of acceptability, and that's fine - one should just know where that is and purchase accordingly.

Every lens has flaws. Some flaws are so common to some lenses, that they even become celebrated as signatures of the lens' character. And this scratch will affect the image in some way, whether you can see it or not. I think the advice you've received is excellent - take some photos in the way you normally would, and have them developed and printed or scanned as you normally would. Look them over carefully and see how you feel. If you see no flaws, then be happy, and if it bothers you, then sell it!

I do wish we'd stop saying things like 'lens has swirl marks' or 'minor cleaning marks' and then assure people that 'won't affect the photos.' Of course it will affect the photos. The only questions are how much and how bothersome will the effects be?

Best Regards,

Bill Mattocks
 
My Nikkor 85/2 and Canon 35/1.8 look like they've been used to get personal with a sandstorm. For my stuff, it matters not at all. Of course, I'm not much for shooting outside.
 
I'm amazed at how well a lens performs with heavy cleaning marks and even chips in the glass. I have been using my Nikon Digital SLR's with LTM to F Mount adapter, suitable for close-up work only. If the lens produces a good image at 6", where the front of the glass is close to the focal point, it will do even better at normal distances.
 
I think I can live with a scatch on the lens if it performs well. I will get the first roll back this evening, but I am fairly certin I will not see anything.

Any thoughts on using a black felt pen to touch up the scratch to reduce glare, anyone try this? Or should I leave well enough alone?
 
I had a Leitz 73mm f/1.9 Hektor at one time, and it had a front element flaw covered with a thin strip of black enamel. It was that way when I bought it and the same when I sold it. The lens was extremely soft wide open, by design. I never saw anything that I could attribute to the covered scratch.
 
I've noticed that the only way to register aberrations and dust/specks/chips and sometimes small scratches on the front lens is to do some macro work with the lens inverted on a DSLR at f22 or more...and then crop 100%.
This way some of my older m49 glass show their age....otherwise....

IMHO: you should keep the lens and use the money you saved to buy and develop more film....and take more pics.... :p
 
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