Featured: 'Natural coating: myth or reality?' by uhoh7

Discussion in 'Open Discussion' started by uhoh7, Dec 23, 2014.

  1. uhoh7

    uhoh7 Leica Place Regular

    163
    Oct 14, 2014
    A few years ago I bought a 1937 uncoated CZJ 50/1.5 with some issues and had Henry Scherer fix it, which he did very well.

    He wrote to me:
    "Hello Charlie,
    I have an opening while waiting for paint to cure while working on a Contax III and so have moved forward with your lens and it is completely disassembled. It is very dirty but very fine. The lens elements are in perfect condition and so my guess is it's going to be a 10 when its done. It's distinguished by very fine surface oxidation of the front and rear lens elements. This shows it's never been cleaned. Whoever owned it previously cared for it very much. This surface oxidation acts like coating and significantly improves the lens so if I were you I'd invest in a UV filter and would never clean this lens. This surface oxidation is very rare and highly desirable."

    Recently a user at RFF found a very interesting converted CZJ 50/1.5 ( http://imgur.com/a/zSQUJ Brian, you will want to check that out) and I related this information, albeit very briefly, at first, in the following thread:
    http://rangefinderforum.com/forums/showthread.php?threadid=146282

    another different user who appears to have some knowledge, though not exactly forthcoming with much detail, basically claims this idea is balderdash in the thread above and I defend the proposition with some more detail....that doesn't impress him much LOL

    Brian, I know you have seen a bunch of these, and other users may have some experience as well. What do you think?

    I did some searching for more info, and found some interesting hints, but less detail and examples than I would like. I.e. it's not oxidization exactly, but exposure to halogens? Some glass will do it and other glass will not?

    This old lens is seriously sharp, and I have not touched it really since Henry cleaned it. Here are some samples:

    15558056075_8bc6e04a67_b.
    L1023014 by unoh7, f/8

    15558890832_101e7a7610_b.
    L1023017 by unoh7, f/9.5

    15371927858_8b7b4d168e_b.
    L1023043 by unoh7, f/5.6

    14947830903_a87d8f74b6_b.
    L1023072 by unoh7, f/4

    These are not edited.

    14932095114_b1574097ea_z.
    DSC02414 by unoh7, on Flickr

    However, for all I know, the guy who claims the natural coating is nonsense may be right...thoughts?
     
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  2. Brian

    Brian Super Moderator Subscribing Member

    Apr 3, 2013
    "Bloom" on the lens is the natural oxidation of glass, acts as a lens coating, and is the phenomenon that led to the application of lens coatings. Look for Neblette, "Photographic Lenses", 1965 edition on Ebay. Great Book.

    It is not present on all lenses, some are better than others.

    http://www.getdpi.com/forum/gear-fs...nnar-custom-converted-leica-thread-mount.html

    So good on this one, I retracted it from sale and kept it. Had offers for full-price after retracting, and made another Sonnar for the person- sold it for $70 less than I priced this on.

    This is the picture that made me decide to keep the lens, wide-open on the M9.

    [​IMG]

    https://www.leicaplace.com/album.php?&u=42

    Now- I did very carefully- clean my lens, front and rear. I keep a very good multi-coated Schneider UV filter over it. Unless it is on the M-Monochrom. Then I use an Orange filter.

    A very special lens in my collection- a 1936 5cm F1.5 Sonnar, factory coated- 190xxxx. I believe that this lens was part of a test run of the vacuum deposition equipment then newly delivered. An RFF member let me know that he had seen another coated lens from this batch, slightly lower SN than mine. This lens had never been worked on when I got it from Ebay. Looked like wax paper when received. My "Naturally Bloomed" lens is from block 198xxxx. I have another uncoated lens from the 190xxxx block within 60 of the one below.

    12575940335_c82a913374_b. 1936 5cm F1.5 Sonnar, coated optics
     
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  3. Brian

    Brian Super Moderator Subscribing Member

    Apr 3, 2013
    H. Dennis Taylor is credited for recognizing that lenses with a dark tarnish (bloom) transmitted more light than a new lens of the same type. Taylor noted his observations in 1896. Source- "Lenses in Photography", Rudolf Kingslake, 1951.

    Neblette also credits H.D. Taylor and writes "The increased light transmission of lenses that had acquired a surface 'bloom' with age was noticed by H.D. Taylor of the firm Taylor, Taylor and Hobson about the end of the 19th century." Source, "Photographic Lenses", Neblette, 1973.

    SO- Kingslake and Neblette are on your side of this argument. Those two have "unTarnished" reputations...

    Not to mention me, just looking at my own "Blooming" lens and comparing it with a coated lens made the same year as it was.

    This is all very transparent to me... I'm on a roll.

    So, lets all sit back and REFLECT on this one... it will all be very clear. Surface weatherization of the glass surface changes the index of refraction, increases transmission, and reduces reflections. Once you get a lens with a good bloom, hold onto it- the rare of the rare.
     
    • Like Like x 3
  4. Mijo

    Mijo Leica Place Veteran

    272
    Apr 11, 2013
    San Francisco
    Jeez Brian, you've probably forgotten more about lenses and cameras than I will ever know. The amount of quality information you provide on this forum is both staggering and generous, thank you.
     
    • Like Like x 1
  5. Brian

    Brian Super Moderator Subscribing Member

    Apr 3, 2013
    Thankyou, it's a hobby. I've been a computer engineer in Optical Sciences for over 35 years. I've had some great optical engineers working for me in the past, learned a lot from them and could ask a lot of questions.
     
  6. dalethorn

    dalethorn Guest

    Amazing stuff!! My reading of Langford's Basic and Advanced Photography in the late 70's didn't mention this at all AFAIK. And any lens that captured that portrait is a star performer.
     
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  7. asiafish

    asiafish Leica Place All-Pro

    Aug 9, 2013
    Bakersfield, CA
    Andrew
    All I know is that my uncoated 1937 Sonnar with mild bloom and my coated 1963 Jupiter 3 (more bloom) are both outstanding, with the J3 far more flare resistant. Not sure if its the actual coating (well worn) or the bloom that makes my J3 so crisp, but it results in a higher contrast image.

    I love them both.
     
    • Like Like x 1
  8. uhoh7

    uhoh7 Leica Place Regular

    163
    Oct 14, 2014
    I'm wondering if a macro shot could capture the oxidation? Is it "oxidization" or another chemical reaction?

    Is it quite apparent to you, Brian?

    and TY so much for detailed reply.
     
  9. Brian

    Brian Super Moderator Subscribing Member

    Apr 3, 2013
    I've read the term "weatherization" used, and recall the term "Oxidation". Looking up the term "tarnish", it is not limited to oxidation and some metals require hydrogen sulfide for tarnish to occur. Both are naturally occurring.

    You can see the bloom on the glass when inspecting closely, can see color in the reflection as it is not as even as a traditional lens coating. You can see a difference when looking at multiple samples of the lens set next to each other. I have 3 uncoated 5cm F1.5 Sonnars tight now.
     
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  10. uhoh7

    uhoh7 Leica Place Regular

    163
    Oct 14, 2014
    TY for that, Brian

    I have to post this wonderful reply by Lightshow in the MFlenses forum:

     
  11. Brian

    Brian Super Moderator Subscribing Member

    Apr 3, 2013
    That piece would certainly explain why some lenses show bloom and others do not. I'll try to get a photo of my 1934 lens, it was the easiest to see the color differences across the surface.

    According to an article, silver requires the presence of hydrogen sulfide in the air for tarnish to develop. The work of Joseph Fraunhofer also demonstrates that might be a cause for tarnish in glass as well.
     
    • Like Like x 1
  12. raid

    raid Leica Place All-Pro

    Apr 12, 2013
    USA
    Raid
    Now I "must" check my old Sonnar lenses for such a bloom.
    I have quite a few old 5cm lenses at home.
     
    • Like Like x 1
  13. uhoh7

    uhoh7 Leica Place Regular

    163
    Oct 14, 2014
    another fantastic post from MF lenses I have to share with you guys:

    There are a number of other interesting comments in the thread:
    http://forum.mflenses.com/natural-lens-coating-myth-or-reality-t69405.html

    One user feels the real effect of "tarnish" would be on the inner surfaces, and wonders if this happens.

    I'm very curious about the chemistry, and would assume there may be multiple processes involved. :) I think we are very lucky to have these 75 year old Jenas and the wonderful M9 to experiment with :)
     
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  14. brusby

    brusby Leica Place Regular Subscribing Member

    96
    Mar 1, 2014
    Great articles, thanks!