measuring registration distance of camera bodies

[Murray@uptowngallery]

If I remove a bayonet-mount lens from an SLR and measure from the front mounting plane of the camera where the lens was removed to the ground glass, I assume this is the registration distance. Does film thickness need to be subtracted to get a 'real number'?

If so, is 0.13 mm for 35mm film right, and does anyone have a number for 120 film? I read 0.2 mm somewhere, but don't know if the film is thicker or if this DOES include the paper backer.

While on the topic, if film thickness has to be subtracted from the 'empty' registration distance, on a sheet film camera with removeable ground glass, I plan to have attached spacer on the glass, and if the film 'counts', I shoudl make the spacer smaller than the ANSI filmholder distance?

Thanks

 

[Nick Zentena]

You need to measure from the film plane. Most cameras I've seen have it marked. It sort of looks like an O with a line in the middle.

Better yet why not look it up? The numbers are mostly on the net some place.

 

[David A. Goldfarb]

Here's a pretty good list--

http://www.a1.nl/phomepag/markerink/mounts.htm

 

[Murray@uptowngallery]

Cuz the one cam isn't listed :O(

Kodak Retina Reflex S

I have a couple loose Deckel bayonets from deceased Schneider/Retina lenses and want to try my hand hacking one onto an orphan zoom lens...

I believe I need to know where the lens belonged (intended target) in addition to the Kodak measurement.

Thank you

 

[Murray@uptowngallery]

A possible answer...Retina lenses supposedly fit Voigtlander Bessamatic and registration for that one is posted on the web.

That Deckel bayonet does look kind of puny however, compared to modern lenses...might vignette...

 

[John Koehrer]

Hi Murray,
You are looking at what is also called "flange to film" distance and no, you don't have to subract film thickness from the measurement.
You can use a depth mic or a simple depth gauge. Mic would be more accurate a range of 1-2" should do for 35mm obviously longer for medium format.
Did you ever get the focus set on the cameras you were working on?

 

[Murray@uptowngallery]

Short answer...no.

I botched a shutter on one (last time, I give up, all I did was take the speed ring off, honest!) and decided maybe since I'm in belated spring-cleaning mode (for once), I'll just unload some stuff on eBay to absorb the cost of CLA. I'll probably still take a look at both the 2nd camera collimation method because it's intriguing me. I already cut ground glass for all the cameras in question, but got kind of disgusted with my Midas touch.