The way a rangefinder calculates distance?

[Compaq]

I sense conflicting information

 

[Helen B]

I sense conflicting information

I don't think there is any conflicting information - what do you see as conflicting? The camera rangefinder 'assumes' nothing, it's just a bunch of cams, gears and levers. The designers design it so that the difference between the rangefinder base and the focal plane is taken into account in the mechanism.

 

[Proteus617]

Compaq- If you lived next door instead of Norway I would head on over and hand you a Graflex. In 3 minutes of tinkering you will have figured out for yourself the RF mechanism including how to adjust it, calibrate for different focal lengths, and re-set infinity stops to correct for differences in distance to the film plane.

 

[Helen B]

Here's a picture of a similar camera - the MPP S-92. You can see the rangefinder cam just in front of the bed hinge at the viewer's left of the camera. Sadly the rangefinder itself is hidden by the side of the camera (it is vertically mounted) and the cam is not the right one for the mounted lens or the bed angle, but you can ignore those small problemettes. If I have time I'll post more examples of rangefinder mechanisms - I'm just about to take a Mamiya Press Universal apart to remove the rangefinder and viewfinder. I'm a huge fan of rangefinder cameras, by the way. Apart from my Leicas, I have a modified Bessa II (6x9, with a modern Nikkor lens), Plaubel Makina 67 and W67, Mamiya 7 II, three Mamiya Press cameras, the MPP shown below, a Polaroid 110B, Stereo Realist, and a Vitessa.

Anyway, that cam moves the lever up and down as the focusing rail moves out and in (the front standard is pulled out to latch in to notches in the bed, so the rail-lens relationship is fixed). When you have the image sharp on the ground glass you can adjust the cam position so that the rangefinder is coincident. The cam and gearing is thus set so that the separation between the image plane and the rangefinder base is taken into account. The cam must be correctly shaped, of course. There is some mysticism over this particular subject, but it is really very simple.

Best,
Helen

 

[Proteus617]

I just googled the S-92. Wow. That's quite the treasure. At first glance I thought is was a Pressman. I wasn't even close. Is that a banana sticker covering up the hole for the RF linkage?

 

[Helen B]

The banana sticker is there to make me a better photographer. It's not something I like other people to find out about, but the #1 photo accessory that will improve your photography is a banana sticker. Tests have proven that it has exactly the same effect as many more expensive gizmos.

I guess that the S-92 must now be the camera I have had the longest. It was my first 4x5, and I bought it when I was a student. I got the whole kit with two lenses (the 89 mm Wray in the picture and a Wray 189 mm f/4.5), wire frame finders, lens hoods, filters, darkslides (filmholders), darkslide case and flash. Sadly I have lost the flash and the darkslide case. I used it hand-held quite a lot until I got the modified 110B.

Best,
Helen