Scratch in the "real world"

[atlfoto]

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Do you think that a 4mm long scratch in the rear glass of a 90 summicron will affect the image quality of a photograph?

[budrichard]

Linear defects on optical lenses are not imaged as linear objects. Each area of the lens contributes to the image as evidenced by stopping down the lens aperture.

But a defect will affect other optical properties such as detail and contrast.

In reality a 4mm defect will probably not be observable in its effect to your eye and probably even with quantative testing which is really impossible because you would have to test the subject lens before and after. I would think that the defect would have more of an effect on the rear lens because it is smaller than the front element.

If you can shoot some test images, that should help answer your question, even better is to compare the lens side by side with another of the same vintage. I shot comparisons of my 90mm Summicron 2nd version along side my 90mm Asph and using K64 under 5x magnification could see no difference.

In the end you will have to make the decision whether or not there is any effect.-Dick

[pgk]

A small scratch is unlikely to produce any visible effect on images. The only time when it might is when you are shooting into the light when it may cause a slight increase in flare. Multiple small scratches do cause problems but a single small scratch is irritating but nothing to worry overmuch about.

[earleygallery]

I agree, it's extremely unlikely to make any difference. I have a quite badly marked Nikon lens, I bought as it was very cheap (in truth I didn't examine it closely enough at it's clearly had a lot of use) and it gives excellent results.

 

If the lens you mention is one you're thinking of buying then I'd expect the price to take into account the scratch, but I wouldn't hold back from buying it on that alone. If the scratch is your own fault and you're wondering what to do, just forget it and keep using the lens.

[atlfoto]

In fact I have already buy it, at a very nice price, but the seller didn't mentioned the scratch at all. I am going to try it and see if it affects the iq. I don't want to return it because I know I cannot pay a better condition (or new) leica lens.

I will revert you the results.

Thanks.

[SJP]

Pictures should be just fine.You could use a black marker pen to absorb the stray light from the scratch but I doubt it would be noticable. With my MATE (tri-elmar 28-50 etc.) I frequently need to enhance the contrast due to flare, and still it is a great lens. This is the "as designed" performance.

 

So I would ignore it. If the pics look OK then the lens is OK.

[cliffp]

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I once put a 3 or 4mm scratch right through the coating on the rear element of a 50mm Nikon F1.4 and it made no difference.

[menos I M6]

I guess - none of the above - "unlikely it makes a difference comments" should be taken lightly as a guide in this matter.

 

None of us here is in the position, to judge, whether the scratch on your lens will have an impact or not.

 

I once bought a 35 Cron ASPH with a small crack on the edge of the rear element.

I oversaw it, as the seller carefully smeared some grease from the lens on the edge.

 

After I found the damage that evening, I shot a test film under various different lighting conditions and apertures and only under certain conditions did I produce ghosts and a very significant band shaped flare.

 

Only testing the lens can give you an informed answer.

[pgk]

only under certain conditions did I produce ghosts and a very significant band shaped flare.

But was this any different from the ghosts and flare produced by a perfect example of the lens? Testing a lens to see whether it is acceptable is one thing but testing it against a perfect example is quite another. I could get similar effects off a perfect 35 asph Summicron if I tried hard. A small scratch is highly unlikely to result is real problems - I have had a few scratched lenses and none have never caused me problems. The question was 'real world' and so were most of the answers.

[menos I M6]

But was this any different from the ghosts and flare produced by a perfect example of the lens? Testing a lens to see whether it is acceptable is one thing but testing it against a perfect example is quite another. I could get similar effects off a perfect 35 asph Summicron if I tried hard. A small scratch is highly unlikely to result is real problems - I have had a few scratched lenses and none have never caused me problems. The question was 'real world' and so were most of the answers.

 

Somebody asks you, if the small screw, he is missing from the used car, he just bought might be of any issue with the potential driving issues it might produce and you tell " a very small screw usually will make no difference in real world driving."

 

How can somebody on an internet forum judge, whether a scratch on a particular lens impacts "image quality" or not without having actually shot it?

 

I tell you, that I experienced otherwise. I, as you, thought the usual scratch will likely produce no issues.

 

I learned different with my own experience. The discussed lens showed no issues, just under certain (not extreme, but certain) circumstances did it produce an optical issue, clearly related to it's damaged rear element.

 

No "real world" experiments or internet myths needed.

[earleygallery]

Menos,

 

The OP asked for opinions, what others here think from their experience. Most of us have said that we think from our experience that a small scratch on the rear element isn't going to make any difference to the end results.

 

Of course there may be exceptions. The actual scratch may be much worse than any of us are imagining for example, or maybe the OP favours contre jour photography.

 

There is a big difference between a scratch and a crack however. As someone else mentioned if the scratch were to cause flare, 'filling' it with some black marker would resolve the problem. I do have a camera in my collection with a crack in the front element - again from my experience it has not caused any problems that I've noticed.

 

Perhaps the OP will be good enough to report back once he's tested the lens.