[This thread was originally a "for sale" posting by Hoyen, but in describing some lenses, he had remarked about the color of the lens coatings. Then came some interesting content that has made this thread important enough to keep (in my opinion, anyway). Then the items sold and Hoyen notified me through email of this so I could delete this thread. So what I have done is removed Hoyen's original posting text and replaced it with this text, and I changed the title and category. Wa la... an interesting thread. -T]

-- Hoyen ~ (simontart@hotmail.com), November 29, 2001

Answers

Response to FS Leica 35mm f2 Summicron-M ASPH

Anyone else ever notice the color of the coatings on their lenses? I'm going to have to check mine out...

-- Jack Flesher (jbflesher@msn.com), November 29, 2001.

Response to FS Leica 35mm f2 Summicron-M ASPH

Yes, there are differences in the color of coatings on otherwise identical lenses. I have two 50mm Summicron Rs, one has a magenta/brown reflection and the other a deep royal blue. Both are mid 80s vintage. There is no discernible difference in photographs. I did ask on this thread some time ago if anyone had any info on what the reason for such differences might be, but no one had an answer. Presumably Leitz (as then was) had their reasons other than running out of raw material for one or the other!

-- Ivor Quaggin (iquaggin@rogers.com), November 29, 2001.

Response to FS Leica 35mm f2 Summicron-M ASPH

I've never noticed any practical difference either but some people have asked for some reason or other. Why the difference is there is anybody's guess.

-- Hoyen ~ (simontart@hotmail.com), November 29, 2001.

Response to FS Leica 35mm f2 Summicron-M ASPH

I've noticed that my various lenses, Leica and otherwise, have differently colored reflections. But it never occured to me that different samples of the same lens could have differently colored reflections. The coating thickness is only a fraction of a wavelength, and I know that the color of the reflection is caused by cancellation of certain wavelengths in the white light striking the lens, due to interference. What puzzles me is that the coating thickness could be allowed to vary so much as to cause cancellation at significantly different wavelengths. Purple is at the short wavelength end of the spectrum, around 400 nanometers, I think; and green is nearer the middle, maybe 500 or 550 nM. Seems to me this would somewhat defeat the purpose of the coatings. Suggests poor quality control. OTOH, maybe it depends on which coating is deposited first, and they just made some changes as they went along. Does anyone have more insight on this?

-- Bob Fleischman (RFXMAIL@prodigy.net), November 29, 2001.

(just to bring this to the top of the recent answers list because not everyone would have read this originally "For Sale" thread, yet now it has interesting content.)

And now I've got to check my lenses to see what color they are! :-)

-- Tony Rowlett (rowlett@mail.com), December 18, 2001.