LF Rangefinder distance scales, is it to nodal point or film plane?

[Vick Ko]

Just wondering, as I'm calibrating my Crown Graphic rangefinder image to the ground glass image.

Is the marked distance scale to the film plane, or the nodal point of the lens (and I suppose, to which one, front or back)?

For a 135mm lens, it might make a difference, since that is over 6 inches, so on the engraved scale, it is over the "line width" of the index mark.

Not that I'd scale focus, but it is a question I had.

[E. von Hoegh]

Film plane, always film plane - whether LF, 35mm, etc.

[photobymike]

You do know that just cuz an Optar says 135mm does not mean it actually is.... in my investigation of setting the rangefinder and distance scale i found that the Graflex lenses varied so much that that the made 20 or 30 different scales to match the lens... oh yea and the lens cams had to be cut to match the lens.... Linhof did this also. Linhof cams even were stamped with the len serial number for a mated pair ... The Technica guys knew this..... not so lucky with the Graflex. and the distance scales well i have attached a chart to show the different scales and part numbers. There is light at the end of this tunnel...there is a guy here on LF that will cut any cam to match your specific lens. woohoo "I just want to take pictures; i do not want to work on cameras".... oh and them there is another discrepancy with the ground glass with what back casting... oh groan.... some used a fresnel and some used a product called Ektalite <probably when they were owned by Kodak. This changes the back to film measure by up to 3mm ... so when you focus with your magnifier and then you take a picture that is out of focus. grrrrr frustrating. I sold my graflock back cameras and i bought and original camera with a spring back.... and a Kalart rangefinder < they do not use cams and be adjusted for any lens. The spring back does not use a "spacer" or fresnel between the lens and ground glass... simple ground toward the lens.. just glass!!! The spring back holds the film holder in place much more securely.... I have actually accidentally pulled the film holder out just enough to ruin a very important and expensive piece of film. not with a spring back....!!!! Dont get me wrong i think the 4x5 crown is and was the best camera ever made.

http://www.graflex.org/

[Vick Ko]

Yep, thanks all. I read all about Ektalites and fresnel on graflex.org. And cams, and engraved focal lengths not being the actual focal length.

I'm waiting for "Murphy" to do a number on my first films through this camera.

Oh, I want to replace the GG too, it is cracked.

:-)

[photobymike]

There is a guy on ebay that makes them....and spacer glass.....17 dollars i paid....plus shipping.... not bad for the price

[E. von Hoegh]

When replacing the GG be certain to measure (or have measured) the registry distance. Any machine shop can do this in a heartbeat, if you have a real mechanic nearby he/she will also have the ability.

Why leave the door open for Murphy? He's around too much as it is...

[photobymike]

Listen to von... he speaketh truth You can however get your own depth micrometer and measure yourself.... but here is what i found out in my travels ... glass spacer has some properties that make it thinner than it actually is ..... at least that is what the ground glass guy told me.... the fresnel and ektalite also has refraction qualities that change perceived distance versus actual ... oh ok ....well thats why i went to the spring back ...no hocus pocus.....ground glass same distance about 4.7mm that the film is in a holder

[E. von Hoegh]

Listen to von... he speaketh truth You can however get your own depth micrometer and measure yourself.... but here is what i found out in my travels ... glass spacer has some properties that make it thinner than it actually is ..... at least that is what the ground glass guy told me.... the fresnel and ektalite also has refraction qualities that change perceived distance versus actual ... oh ok ....well thats why i went to the spring back ...no hocus pocus.....ground glass same distance about 4.7mm that the film is in a holder

Refractive index of glass is greater than that of air... the same property which makes our lenses work. It makes a .100" piece of glass act like a.066~" shim.
I wouldn't use a glass plate as a spacer, I'd make metal shims to place the glass where it needs to be. Depth mike - http://www.grainger.com/Grainger/MIT...130305183512:s. Not cheap, why I advised to have someone measure for you.

[photobymike]

I bought one these on ebay for 36 dollars and measured it...actually shims are not a bad idea..ok what and how do you make and use shims?

[E. von Hoegh]

I bought one these on ebay for 36 dollars and measured it...actually shims are not a bad idea..ok what and how do you make and use shims?

I use aluminium strips filed to the correct thickness, the same width as the "shelf" the GG sits on.

As for measuring tools, I would not consider buying one used unless I knew who had been using it. Yes, I know they can be verified with gauge blocks... after you've bought them... .