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nonuniform
15-Nov-2011, 12:30
Okay okay last time. I know everyone swears by setting the infinity stops.

One of my Crown Graphics with Top RF has weird behavior - either I can have the rangefinder focus accurately from 6-15 feet, or I have it focus accurately from 15-infinity. Checked against the GG.

So, I've done the infinity stop adjustment, and that seems to get me the 15-infinity focus range.

I'm guessing this is a job for the master cam method of making a mess of my rangefinder?

ps - I have the camera set to focus from 6-15ft, since that's how I use it anyhow, but it's bugging me!

Peter York
15-Nov-2011, 12:49
As I understand it some of these rangefinders have inifinity set at "hard stops," where the focus rail is moved back as far as it can go. Others have infinity set when the focus rails are moved a bit foreward (per the manual). Have you checked to see if you have hard stops or not?

Corran
15-Nov-2011, 15:24
I made a thread about this a little while ago that had a ton of info. Basically it sounds like either you have the wrong cam or the one specific calibration you need a master cam for is out of adjustment (I hope not).

I'm sure much more knowledgeable people will respond than me :)

rjbuzzclick
15-Nov-2011, 16:48
I had the same issue with my top RF SG when I bought it. I couldn't get the RF and GG to agree. Eventually I pulled out the cam to check that it was the correct one for the lens, and it was. When I put the cam back in, it went in with a very solid SNAP sound, it seemed much more solid than when I took it out. After that, it was easy to align, and everything agrees-RF, GG, and focus scale. At least in mine, I think the cam wasn't seated properly. YMMV.

Also, for the record, when set to infinity, the track is not at the hard (all the way in) stop on my camera.

Bill_1856
15-Nov-2011, 16:52
What is a "Master" cam for the TRF Crown? The only ones I know about are the interchangable ones.

Ivan J. Eberle
15-Nov-2011, 17:05
Does it have the balls-in-a-tube actuator like the Super Graphic did? If so, perhaps some of the balls went missing?

nonuniform
16-Nov-2011, 03:27
Do you mean, check and see where infinity focus is set - with rails all the way back, or with the rails moved forward slightly? Hmm. Good point.


As I understand it some of these rangefinders have inifinity set at "hard stops," where the focus rail is moved back as far as it can go. Others have infinity set when the focus rails are moved a bit foreward (per the manual). Have you checked to see if you have hard stops or not?

nonuniform
16-Nov-2011, 03:29
I made a thread about this a little while ago that had a ton of info. Basically it sounds like either you have the wrong cam or the one specific calibration you need a master cam for is out of adjustment (I hope not).

I'm sure much more knowledgeable people will respond than me :)

I totally read your thread! I just wanted to try a logical approach to figuring this out, rather than randomly pulling things apart (tm - how I fixed my Jeep in the desert).

Anyhow, thanks for the ideas. I'm going to try the simpler ones first, and then check for the correct cam, etc.

Neal Chaves
16-Nov-2011, 11:02
I have cut many of my own cams for TRF Crowns, and Linhofs before that. I have never heard of a "master cam" for TRF Crown. I do know that most factory TRF cams are not as accurate as they could be. The cam shape for most lenses will be a curve, which indicates that focusing is not linear.

When hand-cutting a cam, a number of focus targets are set up at distances from the closest practical to "infinity", and the curve is developed and smoothed out. When doing a careful job, it may come to two or three final passes of a very fine file at the end.

In answer to your specific question about the cam not being accurate throughout its range, you can try the following. At the point where the split image does not indicate the accurate focus on the GG, it the image is short of coincidence, the cam curve is low. If the image goes past coincidence, the cam curve is high. Get in there with a Sharpie pen and mark the location of the follower on the cam.

If the cam is high at that point, you can simply make a few passes with a fine file in that area and then check focus again. If the cam is low at any point in the curve, you can "stretch" it a bit by tapping with a hammer and punch on an anvil in that area and then finish with a fine file. If you ever see any old Linhof cams, you may find some with these "stretch marks" from the factory.

Attached is a photo of some of my TRF cams, cut from hobby shop brass stock. 250, 150, 90 and 65mm.

Robert Meier
16-Nov-2011, 11:39
Neal -- you should make these for all of us CG users. Say, 150 and 210 cams. Maybe a 90.

Peter York
16-Nov-2011, 13:17
The master cam is listed in the Graflex top rangefinder service manual. I believe it is used to set infinity on the rangefinder. This is probably an adjustment that, once made, would rarely have to be performed again.

In the end your best bet may be to grab another Crown off of evilbay and sell your existing one.

Steve Choi may be able to help: http://www.stevecamera.com/

Leigh
16-Nov-2011, 14:25
What is a "Master" cam for the TRF Crown? The only ones I know about are the interchangable ones.
The Master cam is a precision spacer that's used to set the infinity position of the rangefinder.

It's dimensional tolerance is quite tight, 0.437" 0.0001".

And to those who have "never heard of a Master cam", RTFM. It's discussed prominently in the instructions.

- Leigh

nonuniform
16-Nov-2011, 16:21
Yep, I read the manual!

In reply to Peter:
I have two Crown Graphics, both in really nice shape, and except for the fact that one of them has a focus glitch, they both work. You may not have seen the original post, but I have the camera set to work the way I use it, but I just decided that I might actually try and fix it properly.

Thank you everyone for your thoughts.

Neal Chaves
17-Nov-2011, 15:48
I think Midwest Photo Supply re-manufactured some TRF cams about 15 years ago. That they don't sell them now suggests that the demand is not there. Every lens, even lenses from the same manufacturer and design is different. This is why Linhof serializes every lens and cam.

The TRF Crown is capable of outstanding focus accuracy but cams must be custom cut for each lens.

Ivan J. Eberle
17-Nov-2011, 16:19
So the same cam and same lens transferred to the other body works?

Leigh
17-Nov-2011, 16:25
So the same cam and same lens transferred to the other body works?
Assuming the receiving body is properly adjusted (with a Master cam) and undamaged, the new lens/cam should work properly.

- Leigh

Neal Chaves
18-Nov-2011, 17:16
I just RTFM and found mention of the Master Cam. I have been repairing TRF Crowns and cutting cams for a number of years before obtaining this manual. My 1965 copy says that the adjusting procedure had just been changed. I also see the procedure involves setting the camera up on what have been called "soft stops" and I personally do not like that. I don't favor Technikas anymore, having had three, but I want my TRF Crowns set up on "hard stops" like a Technika.

The TRF Master Cam should be easy to make, much easier than making a cam. My current TRF Crown was probably unused original when I got it and I have never touched the mirror mechanism. It lined up perfectly at infinity with the original lens and cam on hard stops. There is one more infinity adjustment and that is the plunger arm down on the left inner track. I can't find any mention in the manual of how this arm should be fitted. I have never touched it.

I measured my 250 cam because it is the flattest. It looks like 0.437" to me at the point where the cam follower rests at infinity (hard stops on my camera). I cut the cam that way. I have had many TRF Crowns of my own and worked on those of my friends and I have never seen satisfactory (for me) operation of multiple lenses on the same camera with factory cams.