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Kevinc
Tinkerer
Username: Kevinc
Post Number: 4
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 07, 2009 - 08:53 pm: | 
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I think my Olympus OM-10 has a bad view finder and I'm not 100% sure why it is. I've tested focus using Rick Oleson's methods for focusing on infinity and confirmed that when the lens is set to infinity (pointed to a far away object), the focal plane (film) is crystal sharp. However the viewfinder indicates otherwise.
You see, when I use the viewfinder to point to something really far away (airplane, cloud, etc) and match the split screen, the lens indicates that it is only 10 meter away. On the other hand when I set the lens to infinity and I point to those objects, the split viewfinder doesn't match up.
I've ruled out the possibility of badly installed focusing screen as I've tried 2 different focusing screens (new, old), each on both sides (apparently only one side of a focusing screen can be used). So now I'm guessing the root cause could be the penta-prism, thought I'm not 100% sure.
If my guess is right, is there a way to adjust the distance between the mirror and the penta-prism? Any insight to this would be greatly appreciated!
Kevin |
Bossman
Tinkerer
Username: Bossman
Post Number: 58
Registered: 02-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 07, 2009 - 11:13 pm: |
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Here's what you do! Get a piece of ground glass, cut it to fit exactly in the film path/track; set camera to "B" or "T" if available and open shutter. Rack lens to inf. and if 100% sharp (use eyeloop or mag. glass) you then have established that the actual focus thru the lens and onto film surface is correct. Then check thru your VF........if off you then have to adjust the mirror distanct to focus screen OR adjust he screen itself (depends on the camera design. Further info? Art www.flcamerarepair.com |
Kevinc
Tinkerer
Username: Kevinc
Post Number: 5
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 08, 2009 - 12:37 am: |
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Hi guys, I found out what caused the focus problem. I was trying to be clever-- I tried to dampen the sound of the mirror coming back by adding a little piece of cloth between the mirror and the stopper.
Apparently, even 0.5mm of cloth can offset the focus! I took the cloth out and now everything focuses perfectly (e.g. the lens-to-focal-plane distance is now equal to the lens-to-mirror-to-focusing-screen distance). I should have known better.
Learning something new everyday...
Kevin |
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