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?
Attachments
Spyderman
Well-known
The words about complicated construction perhaps reffer to focusing helicals... But the optical block can be easily separated: just grasp the front part and unscrew it from the focusing block (part).
Then you can just play with the optical part. Also, if the lens has stiff focussing you can try cleaning and relubing the focusing part. (see the repair manual at http://www.pentax-manuals.com/repairs.htm )
IMHO you should tr to clean it. At least I would do so. I just can't stand having any dirt in lenses, in viewfinder, on focussing screen, ... and anywhere on camera. For this reason I already damaged some of my cameras... I just can't leave it be, even when it's working fine. :bang: But if you have another Jupiter on the way - why not try to clean this one ?
Then you can just play with the optical part. Also, if the lens has stiff focussing you can try cleaning and relubing the focusing part. (see the repair manual at http://www.pentax-manuals.com/repairs.htm )
IMHO you should tr to clean it. At least I would do so. I just can't stand having any dirt in lenses, in viewfinder, on focussing screen, ... and anywhere on camera. For this reason I already damaged some of my cameras... I just can't leave it be, even when it's working fine. :bang: But if you have another Jupiter on the way - why not try to clean this one ?
ferider
Veteran
Once you have separated the front from the focus mount, you can split the front into two parts, (1) before and (2) behind aperture, by simply unscrewing the small lens block in the rear of the lens (by hand). That way you can get at least to the two element surfaces next to the aperture.
If your spot is not there it becomes a little more complicated.
Roland.
If your spot is not there it becomes a little more complicated.
Roland.
oscroft
Veteran
Aha, I hadn't realised it was so easy to separate the lens assembly from the focusing assembly. Once I did that, I discovered it wasn't fungus or bubbled balsam at all - it was just a grease smear! And it was definitely worthwhile splitting the lens assembly into the two parts - inside I discovered a lot of very thin oil (I don't know why anyone would try to oil in there - it's not a moving part), and some of the oil had run around the edge of the inner glass element (though none on the diaphragm blades). The focus was already quite smooth (not too stiff, not too loose), so there was no need to open the helicals for a lube.
So, I now have a much cleaner old J-9, which I'll take out again next weekend (and today I also have an even cleaner, mint condition, 1977 J-9 in black, which I'll also have to test).
Thanks again.
So, I now have a much cleaner old J-9, which I'll take out again next weekend (and today I also have an even cleaner, mint condition, 1977 J-9 in black, which I'll also have to test).
Thanks again.
Spyderman
Well-known
congratulations 
J-9 is a great lens if you don't get a dog (appologies to all dog-like animals).
J-9 is a great lens if you don't get a dog (appologies to all dog-like animals).