Optical Engineers/Glass Experts: Advice on lens damage

[Arvee]

I have on occasion run across lenses offered at really good prices that have cleaning marks/scratches/abrasions on the front or rear lens surfaces.

For the most part the ones I grabbed had problems with front surfaces but that had to be pretty bad before it was noticed on the neg, usually in the form of flare/ghosts.

My question is: Damage to which surface will be more readily seen on negs, front element or rear element? Or does it really matter?

I once purchased a dropped 50/2 Summicron for $5 and black lacquered the moon shaped crack on the edge of the front element and used it for many years with no noticeable effect other than it was probably an f2.2 lens. Ugly as all get out but print for print it matched just about anything out there!

-Fred

 

[Steve Smith]

I'm neither an optical engineer or a glass expert but I think that scratches will show up as increased flare rather than actual marks on the negative.

scratches, and even air bubbles, are so far out of focus that they will not show up as individual entities in an image.



Steve.

 

[Arvee]

So which is worse, front element damage or rear element damage? I seem to recall reading rear element damage is substantially worse.

-Fred

 

[2F/2F]

I think I remember reading rear element damage is substantially worse.

-Fred

That's what my camera repair guys have told me.

 

[Christiaan Phleger]

Rear is worst, more negative effect with smaller damage. Nicks can be dotted out with very black ink, actual scratches or gouge can be really bad, especially on wides. Fronts are much less serious, shooting situations where a bit of flare from cleaning/coating marks usually can be worked around or avoided, tele's are more resistant to abuse. I've seen a Nikkor 200/2 with a completely translucent quarter sized patch of well worn front element glass, the lens was still sharp.