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  1. #21

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    Quote Originally Posted by randy6 View Post
    I do a lot buying from different sources and different parts of the country. I almost allways see issues with angenieux, steinheil and some older leica lenes.
    Because...............over the years they have been under many different owners and stored in many different conditions. Ipso facto they will exhibit many traditional problems if any one of those owners has unwittingly started the deciline. UV light is the best thing for older lenses, not a drawer.

    Steve
    http://www.flickr.com/photos/steve_barnett/

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    landscape photographs in and around the Peak District National Park, UK.

  2. #22

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    Uncoated lens are prone to scratches. Coated lenses added a hard layer that protected the glass.

    I think that's why uncoated lenses get the reputation for being "soft." Optical glass can't really be soft. Otherwise, it would bend and melt if left in a hot car.

    The thing with uncoated lenses is how they were handled over the years. Aggressive cleaning has caused many to have "surface cleaning" marks, which are just minute scratches. I've had several lenses that have been damaged by this.

    There also is a natural process called "blooming," which affects some uncoated lenses. The result is that it can help to reduce intralens reflections, although it doesn't protect the lens like anti-reflective coating does.

  3. #23

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    Quote Originally Posted by E. von Hoegh View Post
    A Sonnar, with all it's internal sufaces, benefits from coating - the more internal surfaces, the greater the benefit. Most modern lenses would not be useable without antireflective coatings.
    E, have you seen a Sonnar cross-section? 6 air-glass interfaces, the same as the highly flare-resistant Tessar.

  4. #24
    Ian Grant's Avatar
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    Quote Originally Posted by elekm View Post
    Uncoated lens are prone to scratches. Coated lenses added a hard layer that protected the glass.

    I think that's why uncoated lenses get the reputation for being "soft." Optical glass can't really be soft. Otherwise, it would bend and melt if left in a hot car.

    The thing with uncoated lenses is how they were handled over the years. Aggressive cleaning has caused many to have "surface cleaning" marks, which are just minute scratches. I've had several lenses that have been damaged by this.

    There also is a natural process called "blooming," which affects some uncoated lenses. The result is that it can help to reduce intralens reflections, although it doesn't protect the lens like anti-reflective coating does.
    That's not strictly true, I have many old uncoated lenses and the glass is fine with no scratches. However some of the 1930's lenses used newer glass from Carl Zeiss/Schott that seems to be prone to scratches and atmospheric attack. The lenses I've seen like this are Summars, some Tessars and Novars and it's due to the glass being softer.

    Ian

  5. #25

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    I have always wondered what would be entailed in coating lenses at home. Seems like a handy fellow could do some sort of coating.

  6. #26

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    Quote Originally Posted by Tom1956 View Post
    I have always wondered what would be entailed in coating lenses at home. Seems like a handy fellow could do some sort of coating.
    Vacuum pump, bell jar, magnesium flouride and a way to vaporise it within the bell jar, temperature controlled oven to bake (harden) the coating. Miscellaneous stuff to clean and prepare the glass, as well as facilities to de- and re- cement lenses.

    I think it's doable, if someone wants to devote the time and effort. I want to try it, I've had good success silvering a telescope mirror... only took two tries.

    Lenses you don't value to practice on.
    Oh yes, a lot of skill and time to practice.
    Last edited by E. von Hoegh; 06-01-2013 at 01:05 PM. Click to view previous post history.

  7. #27

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    Quote Originally Posted by Dan Fromm View Post
    E, have you seen a Sonnar cross-section? 6 air-glass interfaces, the same as the highly flare-resistant Tessar.
    Yes I have. I've also used coated and uncoated Tessars, I much prefer the coated ones. Dagors, Protars, and Rapid Rectilinears are about the only uncoated lenses I've used which I like, all have two internal surfaces rather than the Tessar's four.

  8. #28

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    Just seems like something I could do. Time and again in my life I've undertaken service, repair, restoration projects on, that I had previously never even seen done; and ended up with expert-quality results. It's all in the mentality I suppose. I've always held a standard for myself that there's 2 grades of work--perfect or knucklehead.

  9. #29

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    Just another dumb idea I'll never have the money to fool with.

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