Enlarger lens scratched, silicon fix?

[zesbaugh]

Just aquired El Nikkor f2.8 for a song, small problem in that rear element has some fine "cleaning" marks.
Thinking about using some of that silicon windshield treatment to minimize them. Anybody else tried this before, am I going to further ruin lens?
Will very fine scratches even make a difference on rear element, should I leave well enough alone??

 

[naeroscatu]

Why don't you test the lens on a clear negative before using any treatment on it. Focus the lens on the grain and make some prints from the clear negative, any marks should show on a black print.
Not sure if windshield treatment will work for lenses, I would not try something like that. If we are talking cleaning marks and not scratches, I assume you will not see a difference.

 

[Ian Grant]

Try it as it is, it's probably fine.

Ian

 

[Arvee]

Ian's right. I have a Minolta lens that has some obvious scratches on the rear element. Absolutely no evidence on the print whatsoever.

I am pretty sure the silicone stuff you're talking about will screw up the lens beyond repair.

-F.

 

[zesbaugh]

New I went to the right place, thank you all! Will leave it be and do some testing. All of my other optics are pristine so those tiny little scratchs look like the Grand Canyon to me, but "If it ain't broke..." seems to be true as usual.

 

[Anscojohn]

New I went to the right place, thank you all! Will leave it be and do some testing. All of my other optics are pristine so those tiny little scratchs look like the Grand Canyon to me, but "If it ain't broke..." seems to be true as usual.

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If any thing, I would expect a slight--very slight--lowering of contrast, rather than any scratches appearing; if I am correct, it would be correctable in printing.

 

[zesbaugh]

Why don't you test the lens on a clear negative before using any treatment on it. Focus the lens on the grain and make some prints from the clear negative, any marks should show on a black print.

Would there be any grain to focus on with a clear nengative?

 

[Ian Grant]

No

Ian

 

[Dave Pritchard]

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If any thing, I would expect a slight--very slight--lowering of contrast, rather than any scratches appearing; if I am correct, it would be correctable in printing.

This sounds like a quote from my darkroom mentor, Henry Sapp, years ago. I asked him about a lens with some scratches on it. His reply, "Slight local loss of apparent contrast. You'll never notice it."

 

[ic-racer]

If there is any base fog, there will be grain ( base fog is, of course, grain).

 

[GJA]

If there is no grain, just scratch the negative, and you will have something to focus on. Same thing with a pure black frame too.