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Crown Graphic Top Rangefinder Adjustment

aconbere

Subscriber
Joined
Aug 2, 2023
Messages
401
Location
Seattle, WA
Format
4x5 Format
Hi all,

My crown graphic with top rangefinder came with an accurate but vertically displaced rangefinder patch. I tried to adjust it today and I am BAFFLED.

I have been searching for any documentation on adjusting the stationary mirror and coming up blank. Hoping someone here might have some ideas.

The device seem to involve a screw on one side that is then used to pivot the mirror over a set of ball bearings precariously perched under the mirror plate? It’s pretty weird.
 

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As I recall, there is a set screw on the shaft of the rotating mirror, located inside the camera body, which locks both the vertical and rotary alignment. It's awkward to reach, and requires lots of trial and error to set correctly. Hopefully someone with a fresher memory can expand/correct.

That reminds me, I need to get around to adjusting my rangefinder.

Edit:
This is the reference that I use. https://lommen9.home.xs4all.nl/cams/index.html
 
Huh… makes me wonder if there’s something else going on with this rangefinder.

When I opened it up there were two small ball bearings positioned between the plate the stationary lens sits on and the rod it’s attached to.

When the adjusting screw is loosened even a little the mirror sits loose.

Maybe someone had tried to correct that by jamming a couple bearings in there to wedge against.
 
The bearing balls are part of the rangefinder. I had a vertical displacement that (I think) I corrected by gently pushing up or down on the big black arm, didn't take much IIRC. The half silvered mirror in one of mine required me epoxying in a replacement. These are great cameras worth some time and money. The battery doors go missing, put a couple AA batteries in and push the red button and enjoy the ability to focus in the dark
 
Yeeesh now I can get the patch roughly in the center (I shimmed up the far edge of the fixed lens with some layers of tin foil). However the coincident image is WAY off.

I’m gonna has to spend some more focused time with this tomorrow.
 
Ah! The ball bearings ARE part of the static mirror assembly!

I don’t see those indents and detents in mine but maybe if I took it all the way apart I would.
 

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Okay! One other issue is that the moving mirror is missing one of its clips and unless put in with care moves a bit.

But with the static mirror correctly assembled I get a mostly in the center patch that is vertically aligned.

However… the rangefinder is quite a bit off now . Does not focus correctly at infinity at all. At 10 feet it reads about 15.

So I guess I’ll learn about those adjustments later today and check that the cam is correct for this lens.
 

I might have fixed mine by accident. I had to epoxy my fixed mirror back, it had fallen off. Someone had superglued it in place 30 years ago, the little metal clips were absent.
 
How important is the master cam to get the rangefinder adjusted (assuming I’m not swapping in multiple cams?)

I don’t have a master cam, but I am comfortable just setting the rangefinder infinity for the one cammed lens I have.
 
well, I went ahead and just adjusted the rangefinder for the cam that’s in there. Set it at infinity, dialed in nicely, repeatably accurate against the ground glass. Focuses nicely at close focus, tack sharp.

Guess that wraps this up

Thanks for the help everyone.
 

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