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Message |
    
Ciccone
Tinkerer
Username: Ciccone
Post Number: 5
Registered: 02-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 26, 2009 - 10:33 am: | 
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hi everyone,
here's the plot: i want to check that my little rangefinder (an olympus 35RD) focus correctly on the film plane, does someone have a tip to check this on a (quite) cheap manner. i thought about using a piece of tape or some kind of tracing paper, but i think this method would not be very accurate, what do you think of it?
thanks a lot for your answers |
Glenn
Tinkerer
Username: Glenn
Post Number: 505
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 26, 2009 - 05:26 pm: |
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Get yourself a nice sunny day, a brick wall, tripod and camera loaded with film, surely I don't have to go into any more details. If you also measure the distance from the wall to the film plane with an accurate tape, you can also check that the focusing scale is reasonably accurate. Just check the resulting negatives with a good magnifier and remember to always use maximum aperture to expose them. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 778
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 26, 2009 - 07:26 pm: |
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or, http://rick_oleson.tripod.com/index-123.html |
Geowelch
Tinkerer
Username: Geowelch
Post Number: 19
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 26, 2009 - 08:27 pm: |
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You can make a sort of "ground glass" or focus screen for the camera with frosted "invisible" tape stretched across the frame opening with the back of the camera open. Use a lupe magnifier to check the focus against the rangefinder. For larger medium format rangefinders use a piece of plastic for rigidity, with the tape on one side for the test focus screen. I used part of a sacrificed CD jewel case. for this and it works quite well. |
Charlie
Tinkerer
Username: Charlie
Post Number: 192
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 27, 2009 - 07:09 am: |
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The tape should be on the lens side of the plastic and the platic against the film rails |
Geowelch
Tinkerer
Username: Geowelch
Post Number: 21
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 27, 2009 - 11:18 am: |
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Exactly Charlie. |
Connealy
Tinkerer
Username: Connealy
Post Number: 13
Registered: 02-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 28, 2009 - 06:34 am: |
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In my experience Rick's method for checking the infinity focus of a lens is a lot less ambiguous than trying to determine focus accuracy with a ground glass. A ground glass image permits one to detect the difference between an image that is in focus or grossly out of focus, but when you get to the fine tuning part, the grainy lack of resolution of the ground glass gets in the way.
Mike Elek's site has another good illustration of the technique described by Rick.
http://elekm.net/zeiss-ikon/repair/collimate/
I have found it a help to use a 135mm telephoto on the slr to view the target. |
Bill_alexander
Tinkerer
Username: Bill_alexander
Post Number: 15
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 28, 2009 - 10:26 am: |
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I have in the past been successful by getting
a piece of ground or frosted glass from the local
glass shop cut to the size needed and putting on
the film plane and setting the focus like a view
camera, A little work but with good results, I keep several sizes for all my cameras. |
