Results 1 to 7 of 7

Thread: Separation?

  1. #1

    Join Date
    Oct 2010
    Posts
    571

    Separation?

    I always do research before I ask the question here but the forum provides the best info . So , is separation a red flag when considering a lens ? What exactly is separating and does the separation continue to get worse with time?

  2. #2

    Join Date
    Sep 2007
    Location
    AZ
    Posts
    4,423

    Re: Separation?

    Good question that should have a thread. Most lens designs cement or glue pieces of glass together. For more than a hundred years, they used Canadian Balsam to do this. Sometimes, the balsam becomes crystallized or otherwise starts to release. Often seen at the edges as a yellow ring partially or fully around. I wouldn't worry about this type. It does not seem to increase in a few years or even a decade, in most cases. I've got a lot of lenses from the 1850s that have a little edge separation. If that's the worse it can do in 160 years I'm not too worried.

    Sometimes the lenses start to separate in the main part of the lenses, as a yellow or white or black spot or feather appearance. The latter indicates the separation might be growing. Either way, any obstruction in the center of a lens starts to reduce contrast and can be less than ideal. A small dot or two on a large format lens I wouldn't worry about. Large amounts that cover, say, 20% of the glass will be a problem. The solution is to re-cement them, an expensive repair unless you do it yourself. And few do.

    How to prevent separation? The type, thickness, and application method varied between manufacturers. You won't see many Voigtlanders separated, for example. But you will see a lot of Gundlach Turner Reich that are. I also believe years in the hot sun, such as in a window display, or other temperature variations may contribute to separation. Finally, don't clean the edges of your glass with strong solvents, which can start to wick into the seam.

  3. #3

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    8,260

    Re: Separation?

    John, it depends on the separation. Three examples:

    16/2.5 Luminar with balsam piled up around the periphery of the front element and major voids between the formerly cemented elements. The lens appeared to have been baked, front down. Less than half the resolution, by test, of a known good 16/2.5 Luminar and miserable contrast.

    58/5.6 Grandagon with silver spots in the rear cell and rings of fire in both cells. This is a modern lens made with, alas, the wrong modern synthetic cement. Looks like hell, shoots quite well.

    Kodak 25-15 converter for the 25/1.4 Cine Ektar II. I have one with magnificent Newton's rings that can be seen through my Beaulieu's finder and on footage shot with it. Completely unusable. I'm not sure what the cement is.

    Garrett, watch what you say about Voigtlaender lenses. In modern times V used what seems to have been the same wrong synthetic cement as Rodenstock. I have a couple of Apo-Skopars with spectacular rings of fire in the drawer.

  4. #4

    Join Date
    Sep 2007
    Location
    AZ
    Posts
    4,423

    Re: Separation?

    I'll watch out. You know about the modern stuff more than I do, I was thinking of old 1800s ones.

  5. #5
    Jim Jones's Avatar
    Join Date
    Aug 2006
    Location
    Chillicothe Missouri USA
    Posts
    2,933

    Re: Separation?

    I've used an inexpensive Symmar with edge separation. The images at small apertures are fine.

  6. #6

    Join Date
    Nov 2006
    Posts
    218

    Re: Separation?

    Quote Originally Posted by goamules View Post
    I'll watch out. You know about the modern stuff more than I do, I was thinking of old 1800s ones.
    The post-WWII Apo-Lanthars, Apo-Skopars, and small format 50mm Septon, are all highly prone to separation. These seem to be the only Voigtlander lenses affected by significant separation most of the time.

    By the way, I have repaired a couple Voigtlander Petzvals with very bad balsam degradation (front lens of course)

    cheers

    Tim

  7. #7

    Join Date
    Mar 2008
    Posts
    361

    Re: Separation?

    Quote Originally Posted by John Conway View Post
    So , is separation a red flag when considering a lens ?
    Separation can change elements alignment in a lens. I think you already know, what that can mean.

Similar Threads

  1. lens separation help
    By lenser in forum Lenses & Lens Accessories
    Replies: 9
    Last Post: 24-Apr-2012, 12:32
  2. Is this separation?
    By Brian Ellis in forum Lenses & Lens Accessories
    Replies: 6
    Last Post: 10-Jan-2011, 16:37
  3. What is this separation?
    By kissssss in forum Lenses & Lens Accessories
    Replies: 9
    Last Post: 18-Jan-2010, 02:10
  4. Cloud Separation
    By chris_4622 in forum Style & Technique
    Replies: 23
    Last Post: 5-Apr-2008, 18:18
  5. What is this, separation?
    By patrickjames in forum Lenses & Lens Accessories
    Replies: 14
    Last Post: 9-Dec-2007, 20:31

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •