Whats the best way to measure the 28.8 mm distance

[howpow]

Hi Folks, I have a Fed 2, Fed 3b and 2 Zorki 1's. I have tried to measure the distance from the film plane to the outside of the lens flange which I understand should be 28.8mm. Is there a recommended way of measuring this accurately. My measurements seem to be coming up a bit short of this. Any suggestions ?? 😕

 

[w3rk5]

Check out these sites. They're from memebers of this forum.

http://jay.fedka.com/index_files/Page433.htm

http://www3.telus.net/public/rpnchbck/camera working distance.html

 

[fidget]

Just a heads up for those in the UK, (sorry Howard, no use to you). Aldi are presently selling a vernier caliper for around £8. This is the right tool for this measurement and of course may be handy for a few other measurements too.
Dave.. (no, they didn't pay me to advertise,..... maybe I should ask?!)

 

[w3rk5]

I actually bought a "depth micrometer" for this job.

 

[Buze]

I usualy place a piece of paper (or better, a strip of old film) on the pressure plate before measuring, to make sure the distance to film is not the distance to plate...

I also found that placing something under the pressure plate helps too, it makes the springs stiffer and prevent the caliper from pressing the plate down when measuring.

 

[David Murphy]

Hi Folks, I have a Fed 2, Fed 3b and 2 Zorki 1's. I have tried to measure the distance from the film plane to the outside of the lens flange which I understand should be 28.8mm. Is there a recommended way of measuring this accurately. My measurements seem to be coming up a bit short of this. Any suggestions ?? 😕

If properly used, any decent machinist's caliper can do it. So can a depth reading micrometer (perhaps overkill though). A basic machinist's caliper will hit an accuracy of +/-0.001 inch if used with care (or +/- 0.0254 mm in the metric world).

These instruments take a bit of training to use properly, so if you have never studied machine shop work I suggest asking a machinist friend, or anyone properly acquainted with such skills to help you.

 

[jlw]

A depth micrometer is the way to go. You can use a dial caliper, but it will be hard to get it exactly perpendicular to the film plane, leading to variably inaccurate measurements. (The modified caliper showed on the telus page is a slick solution to this problem.)

When using the depth micrometer, make sure you don't apply so much pressure that you push down the pressure plate. The really correct way to do it would be to press a rigid gauge block against the film rails and then measure down to that, but I have no idea where you'd get a gauge block of the right size.

 

[w3rk5]

The really correct way to do it would be to press a rigid gauge block against the film rails and then measure down to that, but I have no idea where you'd get a gauge block of the right size.

I know the depth gauge was probably an over kill. But it just looks sooo kewl. 🙂

I used a stainless steel ruler to press it against the frame rails. That seemed to do the trick.

 

[howpow]

Thanks for the info guys. Plenty to think about. I'll have to borrow one of the above tools. I have a friend who probably has access to them.