acjeske
Member
I'm looking for someone to help with balsam separation on a Canon 35/1.5 LTM lens. Does anyone do that? Or has anyone tried it themselves?
Mackinaw
Think Different
RichC
Well-known
I did it!
Removed the lens block, put in the oven, ensuring it was level and well supported using a few piles of large metal nuts (don't want elements sliding off!). Then turned the oven on. Can't recall the temp or the time - was over a decade ago - but I'm sure Google will help. May even be an old post on RFF. Anyway, it as Canon 50/1.2, and worked perfectly!
Removed the lens block, put in the oven, ensuring it was level and well supported using a few piles of large metal nuts (don't want elements sliding off!). Then turned the oven on. Can't recall the temp or the time - was over a decade ago - but I'm sure Google will help. May even be an old post on RFF. Anyway, it as Canon 50/1.2, and worked perfectly!
chnops
Newbie
Nice Rich! Question: did you end up separating the elements? Or when you applied the heat, did the balsam melt and re-adhere during cooling?
I did a quick-fix of a 135/3.5 Canon LTM lens: the middle doublet was separated when i got it. $15. The design of the barrel lent itself to the hack, the middle doublet was a tight fit and held in with a retaining ring. I used alcohol to remove the balsam and used index-matching oil for immersion microscopes to repair it. 15+ years ago, lens still works well.
RichC
Well-known
The latter. My theory was that the balsam needed to melt, and the element should sort itself without everything becoming horribly misaligned. And so it proved... Don't get the oven too hot - just enough to melt the balsam. And put the lens in the oven then turn it on - a hot oven might stress a cold lens block, causing damage. And turn the oven off but leave the lens alone until it's properly cold.
I doubt this could make the separation worse. If it doesn't work, you could always try disassembling the lens block and using new balsam/cement/oil.
You could always experiment first by buying a cheap, duff lens. Soviet? Brian ^ can doubtless suggest a few lenses that use balsam...
mothertrucker
Well-known
I had DAG recement a summaron just a couple of months ago for me. He should be able to do it for you.
Freakscene
Obscure member
The Canon 35/1.5 is an uncommon and expensive lens. Probably not the best choice to learn lens repair with. I would contact DAG.
Use a small drop, the surfaces are matched, pushing the group into the barrel aligned it. The oil eliminated the air/glass interface that caused Newton's Rings.
Index Matching Oil- did this over 15 years ago.
Freakscene
Obscure member
I assume the barrel section this doublet fits into is complete, and seals all the way around both elements? Has the lens ever been exposed to very hot or cold conditions? I find this quite remarkable.
Also, how did you match the refractive index? To the glass or the balsam? And is the refractive index of both elements the same?
Thanks,
Marty
acjeske
Member
DAG can do it.
DAG can do it.
OP here. Update: DAG can recement the elements for $225. Might not require that, though. If I go through with it, I'll try to remember to post here.
DAG can do it.
OP here. Update: DAG can recement the elements for $225. Might not require that, though. If I go through with it, I'll try to remember to post here.
The barrel that the doublet fits into is one piece, and is a tight fit. The polished surfaces of the glass doublet are also very tight fits- the
surface tension is enough to hold the elements together with the oil. With the oil- I grabbed what was in the Lab, no careful measurements. "close-Enough"- it works. I've used the lens in Summer and Winter, but "no environmental testing". The lens was $15.
I used Lab grade Isopropyl Alcohol to clean all the old Balsam off the surfaces.
Not to long ago I picked up a second Canon 135/3.5 in LTM, same version as the one picked up almost 20 years ago. Someone advertised it as FL Mount. $10.
ANYWAY! Since I have the lens repaired using the "Cheese-Wiz" method almost 20 years ago, and the one with perfect glass: I took them out on the Olympus EP2.
Repaired lens, wide-open.
F3.5
F5.6
Lens with perfect glass- picture taken about 30 minutes later.
F3.5
F5.6
The EP2 is u43, 12MPixels.
We had an Abbe Refractometer in the Lab: I did not use it. The index of the oil is close enough. The difference between air and glass is big, hence the large reflections and Newton's Rings. The difference between Canada Balsam, Oil, and glass- small by comparison. When I told my optical engineer what I wanted to do- got "Yeah that'll work. Get it right on the first try, because the surface tension is going to make it hard to separate the glass".
ANYWAY! Since I have the lens repaired using the "Cheese-Wiz" method almost 20 years ago, and the one with perfect glass: I took them out on the Olympus EP2.
Repaired lens, wide-open.
F3.5
F5.6
Lens with perfect glass- picture taken about 30 minutes later.
F3.5
F5.6
The EP2 is u43, 12MPixels.
We had an Abbe Refractometer in the Lab: I did not use it. The index of the oil is close enough. The difference between air and glass is big, hence the large reflections and Newton's Rings. The difference between Canada Balsam, Oil, and glass- small by comparison. When I told my optical engineer what I wanted to do- got "Yeah that'll work. Get it right on the first try, because the surface tension is going to make it hard to separate the glass".
For the Canon 35/1.5: DAG would be getting my $225!
Freakscene
Obscure member
Not to long ago I picked up a second Canon 135/3.5 in LTM, same version as the one picked up almost 20 years ago. Someone advertised it as FL Mount. $10.
ANYWAY! Since I have the lens repaired using the "Cheese-Wiz" method almost 20 years ago, and the one with perfect glass: I took them out on the Olympus EP2.
Repaired lens, wide-open.
F3.5
F5.6
Lens with perfect glass- picture taken about 30 minutes later.
F3.5
F5.6
The EP2 is u43, 12MPixels.
We had an Abbe Refractometer in the Lab: I did not use it. The index of the oil is close enough. The difference between air and glass is big, hence the large reflections and Newton's Rings. The difference between Canada Balsam, Oil, and glass- small by comparison. When I told my optical engineer what I wanted to do- got "Yeah that'll work. Get it right on the first try, because the surface tension is going to make it hard to separate the glass".
It seems to look 95% as good as the pristine copy. Nice. Awesome fix.
Marty