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John_s
Tinkerer
Username: John_s
Post Number: 23
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 03, 2010 - 02:42 pm: | 
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It's not really a question, more a report - I bought a beaten up Nikon FM at a camera fair, only when I got it home I realised the focus was way out. The scale showed 1.2 meters when it was focussed to infinity. I found an adjustment on the mirror but only improved it to 1.5 M. The focussing screen although dirty didn't seem to be out of position. Then I noticed a bit of a gap between the mirror and its cradle at one end. I plucked up my courage and inserted a screwdriver, when the mirror was prized off, luckily without breaking. This revealed the problem - a previous owner had reglued it with a thick layer of glue, leaving it much too high in the cradle and causing the errors. I'm in the process of chipping away all the (very hard) glue from the cradle - luckily it came easily off the back of the mirror, and after checking the focus I intend to glue it back on and hopefully get some pictures from a rather battered piece of kit.
Any comments oh how to glue it back and adjust the focus? I should add it's the same with different lenses. |
Prasanna
Tinkerer
Username: Prasanna
Post Number: 57
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 04, 2010 - 08:42 am: |
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I would try placing and focusing it to the right position, first, confirm it several times and then only try and glue it with very thin adhesive. I am surprised that it has to be glued. Usually,in many cameras, there are clips that hold the mirror in place. I don't know the Nikons. Good luck. |
John_s
Tinkerer
Username: John_s
Post Number: 24
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 04, 2010 - 12:32 pm: |
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Prasanna thanks for the comment. There are indeed clips either side. The thickness and hardness of the glue he used meant that the left hand clip was damaged as I tried to chip the glue out, making it useless to retain the mirror, so I broke off both clips and after checking the focus without the glue as you suggest, I have now stuck it back on with a (hopefully) thin enough layer of glue. I will let you know if it's successful. |
John_s
Tinkerer
Username: John_s
Post Number: 25
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 05, 2010 - 05:29 am: |
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Success!After reglueing the mirror I clamped it with a large bulldog clip (protected by tissue paper)to exert pressure as it set. The focus is now just about spot on, with some variation between lenses. The adjustment, a screw to the LHS of the mirror box near the mirror stop, is right at its lowest point.
After seeing remarks as to how delicate mirror coatings are in this and other sites, this poor old mirror has endured so much punishment but it still seems quite serviceable. |
Epatsellis
Tinkerer
Username: Epatsellis
Post Number: 16
Registered: 01-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 12, 2010 - 07:54 am: |
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have you verified focus on the screen vs. the film plane? that should be your final adjustment, ignore the marks on the lens, focus at the film plane to infinity, then adjust the screen/mirror to match. |
John_s
Tinkerer
Username: John_s
Post Number: 26
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 12, 2010 - 02:22 pm: |
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Epatsellis, I have only worked to the lens markings so far - I agree I should be checking the film plane by ground glass etc. I'm accustomed to doing thus on medium format cameras but I'm not confident about doing it accurately with 35mm. I think the best way to finalise the check will be to run a film through it and focus on objects at various distances. Thanks for the comment. |
