What am I doing wrong? Speed Graphic Lens Question

**Erik Sherman** · 4-Jul-2004, 12:58

Richard Ritter's site says that he makes Linhof focusing cams - he might be able to do the same for a Speed Graphic. His URL is http://www.lg4mat.net/.

**tim atherton** · 4-Jul-2004, 14:50

"The focussing cam was/is specially calibrated for the original lens, Not all lenses of the same focal length have the same flange focal length - the distance from the mounting flange to the film plane. The cam will only work with the original lens. Why not use the ground glass?"

I think that most of the Graphics that used cams - either the Super or those with the top mount like the one in question didn't usually have the cams individually calibrated to the lens, unless it was an unusual lens that was outside of the fairly wide range of cams available (though I have had a couple of cams over the years that do appear to have been adjusted). Usually the lens, cam rangefinder set-up was factory/technician calibrated to some extent, but not usually as far as changing the cam though.

However the differences between the actual focal length and the nominal focal length of different lenses of the same focal length eg your 135mm Schneider and optar often isn't so great as to throw the rangefinder focus "way off" as you describe (though it can be - the only way to really tell is do what the technician would do and put them on an optical bench. But more often the difference is say 134.2mm vs 136.8mm or some such. In practice the difference isn't that great

here are the Top rangefinder cams - you can see they make several around the 135mm mark to compensate for this. You should be able to start by at last identifying yours and seeing exactly what focal length for

http://graflex.org/speed-graphic/top-rangefinder-cams.html

The other thing is that in changing around, you may have dislodged the mechanism - check the follow arm is actually travelling along the edge of the cam and hasn't slipped underneath etc.

And do hunt around graflex.org - there are a number of articles oint he rangefinders, setting them up, setting up the infinity etc. And probably similar questions to yours int he list of posts.

As I say, it could be that the actual focal length of your two 135mm lenses is so different that the new one needs a different cam (acutally on checking, the nominal listed flange focal distance of the 135mm 4.5 Xenar was 126mm I think and if yours is the Xenotar, it's 125.3mm - no idea about the Optars, but if it was say 136.6 or something, there is an obvious difference - so maybe try hunt out the cam closest to 125.3mm? - a #2 maybe - just make sure it's a top rangefinder cam and not a supr graphic cam). Or determine the actual flange focal length and then hunt down the right cam (they often show up on ebay etc). Also, someone was building up a library of cam outlines and 1:1 scans to make your own - maybe on photo.net?

**William_4390** · 4-Jul-2004, 16:12

Thanks for all the suggestions. It made no sense to me that each cam was individually calibrated to a specific lens (although I appreciate the input). So, I set the focussing scale to infinity, focussed on infinity through the gg, and now the rangefinder is dead on. Thanks again, y'all.

W.

**Jean-Louis Llech** · 5-Jul-2004, 06:57

A question for Speed/Kalart users :
When you use a Speed Graphic with the adjustable Kalart side rangefinder, does it means that each time you change the lens you have to adjust the rangefinder ?
I don't criticize the system : it seems easier to adjust the rangefinder than to focus the lens on the groundglass if you don't have the assorted cam.
I just wonder if my question is right or not.

**Bill_1856** · 5-Jul-2004, 07:01

Yes, the side Kalart RF has to be adjusted for each individual lens. It's an easy proceedure, but a time-consuming one (maybe 30 minutes).

**Jean-Louis Llech** · 5-Jul-2004, 07:24

Bill, thank you very much for this rapid answer.
I didn't imagine it was so long to adjust the RF. On the field, a cammed-rangefinder system is probably more rapid and easier to use. (I've read the Kalart adjustment page on Graflex.org).
But, if one doesn't change the lens very often, the Kalart system is better, because cams matching exactly the flange focal distance of the lens are hard to find.