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Harlee
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 26, 2004 - 08:05 pm: | 
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I shot some pics with my GSN and they all came out blured - outdoor shots as well as flash shots. I'm assuming the focusing got knocked off or the shutter is staying open longer than it should, but I don't think that's the case, as its locked in at 1/30 when using flash. Whats the best way to adjust the focus? Will setting it at infinity and adjusting the prism correct the problem, or should I take something as a measured distance, say 10 feet, set the rangefinder at 10' and the adjust the prism to coincide with it? I know the prism can be adjusted through flash shoe once the cover is slipped off. |
Jim Brokaw
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 27, 2004 - 12:21 am: |
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Hmmm - you posted twice... I'll only answer one.
Generally you are OK if you set the focus correctly for infinity, comparing the focus with the lens set at infinity (or turned against the stop) and a ground glass (or you can use an old SLR focusing screen) at the film plane compared with the rangefinder alignment split image.
You need to be sure the focusing screen or ground glass is sitting on the film rails, some cameras use a double set of rails to create a 'channel' for the film to run in, and if you bridge the higher set of rails you'll set your focus off. Note too that the focus distance scale on the lens is not necessarily correct either. The correct sequence to do this is 1) set the infinity focus of the lens looking at something far distant imaged on the ground glass (use a magnifier) 2) set the lens to the correct infinity stop - sometimes you need to loosen screws and turn the focusing ring *without* moving the optics until the focus ring bumps against the infinity stop; occasionally this will result in the scale markings not lining precisely up with the index 3) set the rangefinder split image in alignment (generally you set the vertical alignment first, then the horizontal alignment as setting one may throw the other off). Then check everything again and button it all up.
You can also use an 'auto-collimator' to set the infinity at the film plane using a line scribed on a plate of glass and a light shining through from the back... I think there is a web page showing how this can be done using an SLR with a telephoto lens as the viewing device instead of a dedicated auto-collimator. I've done it both ways and if your're careful they yield equal results. |
Harlee
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 27, 2004 - 07:48 am: |
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Thanks,
I thought I forgt to post the first question so I wrote it again and posted it. Sorry! Thanks for the info. Where can a piece of ground glass be acquired, at a hobby shop or something like that. I do have some old SLRs laying around, can the focusing screen be cannibalized out of one of them? |
Jon Goodman
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 27, 2004 - 07:58 am: |
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Sorry, I didn't see Jim's reply or that this question appeared twice. Rick Oleson's page describes the "backsighting" technique of using an SLR to check focus.
http://rick_oleson.tripod.com/index-123.html
Jon |
charlie
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 28, 2004 - 09:29 am: |
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I have used a piece of "invisible" scotch tape on the under sidde of clear glass. |
Jim Brokaw
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 28, 2004 - 11:17 pm: |
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You can make a ground glass by sanding a piece of glass with emery sandpaper (sometimes called 'wet-or-dry') in a random motion. You can probably find it in a good glass store also, perhaps they will give you a small bit, a 35mm size piece only need to be about 1.25" x 1.75", bigger might be hard to handle. I use old SLR viewscreens, from Olympus OM-1 which I have... but use one that is scratched or dirty already, a good one is too delicate and valuable for this use. Frosted plastic might be easy to find, if thick enough to be fairly rigid it will work also. |
Jackson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, July 29, 2004 - 08:25 pm: |
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You can also make frosted plastic from nearly any piece of clear plastic using 400 grit or better sandpaper. It's not pro quality, but good enough to see focus (a magnifier helps). Note that the thickness doesn't matter; the plane of focus is the side nearest the lens. That side always rests on the film guides.
Jackson |
