Cleaning marks inside the lens?

[andrewbuchanan]

I recently got some nice rehoused BNCR cooke speed panchros. The look pretty nice and clean for the most part... however the 75mm has light, barely-there, swirl marks that appear to be inside the lens barrel. I'v never seen this before. I know what fungus and all that other stuff looks like... but cleaning markls inside the lens? The optical coating is flawless, so what is this stuff?

 

I haven't noticed any effect from this when I tested, but I haven't seen the test projected. Should I be wary of these marks? I know pointing any inprefection at a light is a bad idea... but is it possible they function well otherwise? Thanks for any advice.

[Nathan Milford]

The best way to find out is to throw them in a lens projector, otherwise shoot some footage. If you're lucky it won't resolve...

 

It isn't impossible if they're older lenses that a bold previous owner took them apart, or even a clumsy lens tech.

 

Could it be oil? Fujinon has a lens that is notorius for leaking barrel oil into a tryptich of elements. I'm not familliar with the contruction of the Speed Panchros.

 

If it's possible post a picture.

[John Sprung]

Out here, I'd suggest taking the whole set to Clairmont and get them checked out on their projection test system. Sometimes things that look bad to the eye turn out to be not much, and lenses that look clean are way out of whack.

 

 

 

-- J.S.