Calibrating a Rangefinder?

[jakegagne]

<p>Some of you may remember my thread from a few weeks ago about the uncalibrated rangefinder in my Yashica Electro GS. Well, I never got around to returning it to the eBay seller, and figured maybe I could actually fix it. And I did, at least partially! Following the wise Yashica Guy's instructions, I took off the hot-shoe and fiddled with the infinity calibration screw. It now focuses beautifully at 5ft.-infinity, but at close distances is still a bit off. I did some tests this afternoon, and found that an object at: 3ft. is in focus at ~3.2ft/just under 1m., 4ft. is in focus at ~4.25ft/~1.3m, and 5ft.-infinity were all very, very close to being at the correct differences, only a microscopic amount further than the correct markings. Is there another screw for close-distance focusing? Where do I go from here?</p>

[john_shriver]

<p>There may be some adjustment for the "gain" of the rangefinder. It would be something that changed the effective length of one of the arms in the mechanism that moves the moving mirror or prism.<br>

Also, is this from film tests, or just reading the focusing scale? Were you measuring distances to the film plane of the camera?<br>

Also, did you collimate the lens for infinity focus?</p>

 

[jakegagne]

<p>John: This is just from reading the focusing scale, I was measuring about as close to the film plane as I could get with a tape measure, and no I didn't collimate it. How would I go about doing that?</p>

[evan_goulet]

<p>Jake, there is a "zero" adjustment for the rangefinder (the same one that John is mentioning)that can be performed by taking the top of the camera off to get at the nut. If you email through the site, I can send you a diagram of where the adjustment is made. It is done at 1 m from the film plane.</p>

[markus.berndt]

<p>Jake, as far as I remember, there is no extra adjustment to correct close focussing. In fact the only camera that I have ever seen that has something like that is a Fed. Anyway, take a look at the Yashica Guy website, and in particular at </p><p>http://www.yashica-guy.com/document/repair.html#six </p><p>Also, for adjusting a rangefinder, Rick Oleson has posted a fantastic method that does not require a target at infinity, see</p><p>http://rick_oleson.tripod.com/index-123.html</p><p>(Scroll to the bottom of that page) The rest of that page essentially answers your question about lens collimation.</p><p>Good luck and check out the classic camera repair forum at http://www.kyphoto.com/cgi-bin/forum/discus.cgi for a wealth of information of this kind of stuff.</p>

[markus.berndt]

<p>Evan, I had no idea, I would love to see that diagram as well. You must have posted as I was writing my reply.</p>

[steve_mareno]

<p>Congratulations Jake. I have learned the hard way that if you have things this close, leave it be. Can't tell you how many times I've had something "almost there" only to foul it up and have to do everything all over again. And again. I would be very happy w/ a properly calibrated rangefinder from 5' to infinity.</p>

[jakegagne]

<p>Haha, Steve, sounds like a very good idea. I'm just going to take a look and see how much of a pain Evan's "zero" adjustment will be. Fixing that infinity screw took probably 20 minutes of screwdriver insanity.</p>