Haha! Me too, but I'm not sure how quick that will happen. Most of my photo activities have been on hold for the last several months and I still have 7 rolls of 35mm film to print from a late 2019 photo expedition to Italy. I also have two other cameras that are waiting their turn to go on their first local photo expedition. For now, I will probably just shoot a test roll to make sure everything works okay and that the lens is as sharp as it used to be (ie: that I didn't screw it up taking it apart).
I simply based the procedure on what shutterfinger outlined in post #40 of this thread. I don't think it would matter if you put the lens in the oven before preheating it, but I did notice that the preheating raised the temperature higher than the preset value. The temperature near the lens position at the end of the preheat phase (before opening the oven door) was 392F when I did the front pair. For the rear pair it was 377F. The oven may overshoot during preheat knowing that a lot of heat will be lost when the door is opened to place food inside. I'm just guessing, though.Lens will be just fine.
So, the heat treatment is only 30 minutes? Only one heat treatment in the end, or would you recommend two?
Also, why did you put the glass into a preheated oven? Doesn't this increase the chance of the lens breaking up? I thought starting with a cold oven would be safer.
SK Grimes had an article on lens recementing. In it they showed putting the elements on a hot plate at 425°F. Fast high heat may crack the elements or warp the mount barrel.
Preheating the oven minimumizes the time the lens is in direct heat from either the flame in a gas stove or the element in an electric oven.
The lower temperature is safer to both the element and the mount barrel.
One is only trying to soften the Balsum so that it recures, not melt it off.
An oven that heat to 375°F to 400°F on inital heating has a bad thermocouple that reads inaccurately when cold.
I agree. I think it's fair to say that the oven treatment resulted in a stunning reduction in the haze, but my belief that it the haze was eliminated completely was not accurate. It's possible that a longer heating cycle or higher heat might further reduce the haze, but it could also reverse the gains. For example, maybe the repeated heating process causes the old balsam to attack or etch the surface of the glass. I would have to run many more experiments on many more samples to answer these questions and I won't be doing that.You might want to declare victory on this lens and try another! I can't imagine constant temperature cycling won't eventually cause some problem that won't be repairable with even more heat.
Maybe the elements initially need an extended period of high temperature?
Maybe you only get so many chances to affect the change before the cement is permanently altered? Who knows?
It's possible that some lens elements might not ever clear totally, but it sounds like you've made a major improvement.
Thank you.Shear speculation on my part, but maybe the haze is out-gassing of something (residual solvent?) in the Balsam and the heat allows the cement to become malleable enough for the gas to escape. It might be that the temp has to be held for a longer time in order for the gas to entirely exit the join.
But then again, I only speculate...
Good job!
I don't really do portraits, but it did occur to me that this lens could be useful for nighttime small city shooting (street corners, etc) . Sort of like an automatic means of preflashing the film. I'm doing some outdoor and indoor test shots now. I can say that shooting into the sun exacerbates the problem as expected. City lights would likely do the same, but I am curious about what it would look like anyway.If the haze is light and consistent, you may have the perfect lens for portraits and high subject luminence range scenes!
The 127mm and 50mm were both bought new on the same day (1990-ish) and are both Mamiya-Sekor C lenses.The only lens I heat treated was a 12 inch f6.3 Goerz Dagor in a Compound shutter. It did not clear initialy. i had a gas stove at the time, heated the oven, put the lens cell in the center of the oven, turned the oven off, waited until it cooled then repeated the next day. I gave up on the lens and put it away. 3 or 4 months later I took it out and to my surprize it was crystal clear.
Dave are you compairing Fuji Apples to Fuji Apples with regard to the contrast of the 50mm and 127mm? Newer lens have better(?) coatings that produce higher contrast without a change in optical design or lens label.
That's why I switched to 4x5.The RB is a heavy monster
The 127mm and 50mm were both bought new on the same day (1990-ish) and are both Mamiya-Sekor C lenses.
All I can say is that the improvement from the heat treatment was stunning, but the much reduced residual haze is still problematic. The RB is a heavy monster, so I haven't been using it much, but it still looks like new, so this is a disappointment. In any case, I will check the lens again after some weeks or months and see if there is any change. If not, I may try a longer treatment or a higher temp.
I watched the video again and he was using acetone to dissolve the thread locker, as you suggested. He was cleaning the lenses with hydrogen peroxide and lighter fluid (not at the same time, of course). From the videos, it looks like the front and rear lens groups can be removed from Mamiya lenses without much disassembly of the lens body. Since the shutter works fine, I am now seriously considering doing the job myself and have looked up the tools in Amazon. If there are problems with glued element, I'll cross that bridge when I get there.
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