oscroft
Veteran
I recently got an old silver Jupiter-9 - a bit worn, but cheap. I've just shot a test film and there's a problem. At wider apertures the centre of the frame is of very low contrast and looks fogged - see the attached example. At apertures of f8 or smaller the problem isn't there and the pics are fine.
I've had a close look at the lens against a strong light and I can see the problem. On one of the internal elements, there's a crescent-shaped blurry patch about a quarter of the way in from the edge (the position would explain why it only affects f5.6 and wider, I guess). I think this is one of two things - either a patch of fungus, or a flaw/bubbles in the lens balsam. I fear the latter, because I'd expect fungus to disperse the light randomly and cause lower contrast all over, whereas I'd guess bad balsam could direct the dispersed light more directionally?
My problem is what to do, and I'd appreciate any advice. I'd like to try cleaning it in case it is fungus and can be removed (and there is also some dust in the lens - not much, but it could be cleaned out too). But I can't justify the cost of professional cleaning - I could get another lens cheaper (and if it can't be fixed, the money would be wasted). I'm game to try cleaning it myself, but I've read in a few places that the J-9 is mechanically complicated and easy to ruin if you don't know what you're doing.
I could just keep it the way it is and only use it at f8 or smaller, and it really does perform well at small apertures (imagine the attached photo with the centre just as contrasty and crisp as the rest of the frame - that's what it can achieve). I also have another J-9 arriving soon (a black one that I've bought as part of a camera/lens set, described as mint condition), so it wouldn't be a great hardship to reserve the bad one for bright light/fast film/small apertures.
So, what would you do? Does anyone have any references to any maintenance instructions for the J-9, or plans/diagrams for dismantling?
I've had a close look at the lens against a strong light and I can see the problem. On one of the internal elements, there's a crescent-shaped blurry patch about a quarter of the way in from the edge (the position would explain why it only affects f5.6 and wider, I guess). I think this is one of two things - either a patch of fungus, or a flaw/bubbles in the lens balsam. I fear the latter, because I'd expect fungus to disperse the light randomly and cause lower contrast all over, whereas I'd guess bad balsam could direct the dispersed light more directionally?
My problem is what to do, and I'd appreciate any advice. I'd like to try cleaning it in case it is fungus and can be removed (and there is also some dust in the lens - not much, but it could be cleaned out too). But I can't justify the cost of professional cleaning - I could get another lens cheaper (and if it can't be fixed, the money would be wasted). I'm game to try cleaning it myself, but I've read in a few places that the J-9 is mechanically complicated and easy to ruin if you don't know what you're doing.
I could just keep it the way it is and only use it at f8 or smaller, and it really does perform well at small apertures (imagine the attached photo with the centre just as contrasty and crisp as the rest of the frame - that's what it can achieve). I also have another J-9 arriving soon (a black one that I've bought as part of a camera/lens set, described as mint condition), so it wouldn't be a great hardship to reserve the bad one for bright light/fast film/small apertures.
So, what would you do? Does anyone have any references to any maintenance instructions for the J-9, or plans/diagrams for dismantling?
