Kim Coxon
Moderator
Hi Joe,
Can you post a pic of the rear group. From your original description, it didn't sound like a balsam fault to me. Normally, any separation of the doublet will affect only a small area of the group. It will grow over a period of time but my understanding is that it would be rare for the whole group to separate. All of the balsam faults I have seen appear to look more like an "air bubble" in the middle of the glass. I would have thought it likely that if the balsam had gone right across the surface, the 2 elements would have come apart. A doublet is usually made such that the 2 faces that meet should be identical in a "perfect" lens and make a single element. This is never achieved in practice and you are likely to get newton rings where the 2 elements meet. The purpose of the balsm is mainly to fill the very small imperfections and the "glueing" is more of a useful by product.
Looking at Bill's links, it should be fairly easy to tell if it dissolves in xylene. You should be able to get some at a hobby store. Floquil paints used to be xylene based and I am sure there must be others.
Kim
Can you post a pic of the rear group. From your original description, it didn't sound like a balsam fault to me. Normally, any separation of the doublet will affect only a small area of the group. It will grow over a period of time but my understanding is that it would be rare for the whole group to separate. All of the balsam faults I have seen appear to look more like an "air bubble" in the middle of the glass. I would have thought it likely that if the balsam had gone right across the surface, the 2 elements would have come apart. A doublet is usually made such that the 2 faces that meet should be identical in a "perfect" lens and make a single element. This is never achieved in practice and you are likely to get newton rings where the 2 elements meet. The purpose of the balsm is mainly to fill the very small imperfections and the "glueing" is more of a useful by product.
Looking at Bill's links, it should be fairly easy to tell if it dissolves in xylene. You should be able to get some at a hobby store. Floquil paints used to be xylene based and I am sure there must be others.
Kim
bmattock
Veteran
back alley said:
Hey, you're doing better than I am! You don't know anyone else who takes apart the rear element of a Canon 35mm 2.8 LTM lens and puts the lens back together with the f-stops on the bottom, do you? I'm such a moron.
Best Regards,
Bill Mattocks
back alley
IMAGES
greyhoundman said:
ya but, then i'd have to put them back together...
joe
Kim Coxon
Moderator
That is the general idea
Kim
Kim
back alley said:ya but, then i'd have to put them back together...
joe
taffer
void
Joe, why don't you take some different kind of shots with it as it's now, review the results and maybe talk to Ronnie (hoot) later ? He was looking for a very low contrast lens, that Canon could suit him...