How to measure ground glass alignment

[Jordan]

How do you measure alignment of your ground glass? I measured the depth of the film holders first from the face of the frame to the film plane. Then I measured from the inside face of the camera back frame to the frosted side of the ground glass. Does that sound correct?

[SocalAstro]

I would measure

1. From a reference surface on the inside of the camera to the GG

2. Load a film holder with a sacrificial sheet of film, load into the camera back and measure to the surface of the film from the same camera reference surface in step 1 above.

Cheers,
Leon

How do you measure alignment of your ground glass? I measured the depth of the film holders first from the face of the frame to the film plane. Then I measured from the inside face of the camera back frame to the frosted side of the ground glass. Does that sound correct?

[Brian C. Miller]

Remember to check the depth of the film holders with film loaded. I think it's a 0.007-in difference.

[Jordan]

Yeah so is my technique correct? Thanks for the aswers thus far and I did check the depth of the film holder with film in it.

[Brian C. Miller]

Your technique seems to be the same one I used after I replaced the GG in my Super Graphic. I used dial calipers which have a depth guage. Also, check more than one brand of film holder.

[Jordan]

Thanks Brian, I only have one brand of film holder and they're all modern.

[ic-racer]

How do you measure alignment of your ground glass? I measured the depth of the film holders first from the face of the frame to the film plane. Then I measured from the inside face of the camera back frame to the frosted side of the ground glass. Does that sound correct?

Yes, thats how to check. T-distance is a standard, did you get the right number for your format?

[Jordan]

Thanks IC. What is the distance for 4x5? Regardless both depth are the same in my measurements.

[ic-racer]

My notes indicate ANSI Standard (PH3.106.1988) lists "T" distance as:
0.197" +/- 0.007" for 2x3, 3x4 and 4x5
0.228" +/- 0.010 for 5x7
For 8x10, 11x14, and 14x17 holders it is 0.260", 0.332", 0.320", all +/- 0.016".