fabricating wooden camera backs, reducing backs, expansion and enlarging backs

[Michael Roberts]

T-distance is the depth of the film holder from the outside surface of the holder to the film when the dark slide is removed.

The ground glass (gg) should likewise sit in its gg frame 1/4 inch above the surface of the underside of the gg frame that rests upon (contacts) the camera back.

Here are the official (U.S.) standards:

http://home.earthlink.net/~eahoo/page8/filmhold.html

So, .25 inch is roughly (within .001 or so) correct for 5x7 and 8x10. 4x5 is less. (vintage Kodak 7x11 backs are also .25.)

Here are the S&S standards for ULF holders (other makers may vary):

http://ssfilmholders.com/?page=critical_dimensions

[jon.oman]

T-distance is the depth of the film holder from the outside surface of the holder to the film when the dark slide is removed.

The ground glass (gg) should likewise sit in its gg frame 1/4 inch above the surface of the underside of the gg frame that rests upon (contacts) the camera back.

Here are the official (U.S.) standards:

http://home.earthlink.net/~eahoo/page8/filmhold.html

So, .25 inch is roughly (within .001 or so) correct for 5x7 and 8x10. 4x5 is less. (vintage Kodak 7x11 backs are also .25.)

Here are the S&S standards for ULF holders (other makers may vary):

http://ssfilmholders.com/?page=critical_dimensions

Interesting. I own one S&S 14x17 inch holder. The dimensions listed in the chart do not match my holder.

Chart:

A = 1-1/4
B = 19-1/32
C = 15-7/8
D = 3/16
T = 0.335

Measured from my holder:

A = 1-3/16
B = 18-1/8
C = 15-7/8
D = 3/16
T = 0.3195

If the chart is correct, there appears to be some variation!

[Jim Jones]

Jon, the unofficial chart Michael linked to has several errors. Genuine current specifications can be downloaded from http://ansi.org/ for $25. In Michael's chart, the "Depth to Film Surface" dimension quoted is actually the film to septum dimension, the ANSI "T" dimension. This is a .011" error, the width of the film guide slot. This could be a problem for photographers shooting an Aero Ektar wide open, although depth of focus would mask this error at the apertures many of us use. In Michael's chart, the "Exposure Height" measurement is actually ANSI's "D2" distance, the maximum for the film length guide. The "Exposure Width" is also wrong.

[Michael Roberts]

Wow, thanks for the corrections Jim!

[Jac@stafford.net]

Jon, the unofficial chart Michael linked to has several errors. Genuine current specifications can be downloaded from http://ansi.org/ for $25.

True, and I resent the fact that we have to pay for a document of standards applicable to all of us. Please understand that I come from decades of academic experience where so many US government agencies pay for researchers' efforts, and some bumfucked enterprise captures it for $ sake. It is just plain wrong. The professors are also to blame. Something in the system is just plain broken
.
oops! I twisted my ankle jumping off the soap box. But I am serious. We paid for the research and propriety efforts are stealing it.

[zozur]

Hello
Thanks for all suggestions.
Tim - yes it will be great to have another camera for reference, but unfortunately i don't have it. Actually my only part for my diy camera is film holder and everything else will be build from scratch.
Michael - I think I'll choose second option, I have friend with many electric tools, so maybe it will be easier.

I made simple 1:1 2D scheme on plotting paper. Its great stuff for "analog" projects .
Do you think that it look correct?





Here are dimensions:


A - 25mm - 0.984"
B - 50mm - 1.968"
C - 230mm - 9.055"
D - 15mm - 0.590"
E - 35mm - 1.378"
F - 12mm - 0.472"
G - 180mm - 7.086"
H - 130mm - 5.118"
I - 150mm - 5.905"

All the best
Zbigniew

[Tim Meisburger]

Coincidently Michael, I bought an old Polaroid 800 for nothing and have been fooling around in the shop making a wooden 4x5 back for it. Since I have been working out the design as I go along I have been building it up in strips of mahogany, sort of like you describe, although also with rebates cut on the table saw. I should finish this weekend and I'll post a picture then. The film holder will sit in a simple rebate, and be held in place by elastic. The ground glass will be a wooden frame the size of a film holder that will just slip into place. I used a similar method on a pinhole camera and it worked fine.

[r_a_feldman]

I made a 4x5 reducing back for my half-plate Okuhara field camera from thin strips of scrap exotic hardwoods. It fits in in place of the original book-form film holder. Pictures are in post #9 at http://www.largeformatphotography.in...-first-results .

Bob

[Michael Roberts]

Cool idea, Bob. Thanks for sharing!

Beautiful woods....