Wanted - Dimensions of a 5"x7" Film Holder

[Steve Smith]

I would appreciate it if someone with a 5"x7" film holder could take a few measurements for me.

I have seen the table here: http://home.earthlink.net/~eahoo/page8/filmhold.html but do not trust it completely as there are a couple of dimensions which are not quite right on the 5"x4" holder.

I need the overall size, the distance from the inserted edge to the start of the exposed area, the width and height of the exposed area and the dimensions of the tab from the inserted edge (at the bottom on the linked page).

If it turns out that the list I linked to is correct, please let me know.


Thanks,

Steve.

[Jim Jones]

The abbreviated dimensions in the link above differ in these respects from the 1951 American Standard Dimensions for Photographic Double Film Holders of the Lock-Rib Type, Z38.1.51.1951. All dimensions are given in inches.
The cited retaining tab location cited is the maximum. ASA gives the minimum as 7.651.
The cited thickness is the maximum. ASA gives no minimum.
The cited length is the minimum. ASA gives no maximum.
The cited width is the maximum. ASA gives the minimum as 5.875.
The cited distance to exposure field is the maxium. ASA gives the minimum as 0.677.
ASA gives the exposure height as a minimum of 6.579 (big difference!).
ASA gives the exposure width as a minimum of 4.675
ASA gives the depth from the face of the holder to the face of the septum (the "T" distance) as .0228 +/- 0.010.
The ASA thickness of the slot the film rides in is a minimum of 0.012. Thus, the distance of 0.007 film from the face of the holder can vary from 0.213 to 0.231. That tolerance for 4x5 holders is only slightly tighter. No wonder some people fine Aero Ektars unsharp at f/2.5!
.

[Steve Smith]

Thank you. I was surprised at the 7.010" stated for the image height as the film is probably not that big. A gl;ass plate would have been 7" but the film would be a bit smaller to allow it to fit in a septum to go into a glass plate holder. 6.579" seems more reasonable.

The same is true of the height in the 4x5 holder in the ANSI list at 5.002". And as for the 3x4, it is shown at 4.2282 - so almost 1/3" bigger than the film!

One more question: What is the width of the retaining tab?


Steve.

[Jim Jones]

The rib stands 0.055 +/- 0.005 above the surface of the film holder, the angle of one side is 45 degrees +/- 5 degrees, and the flat surface parallel to the face of the holder is 0.046, +/- 0.005 long

[Steve Smith]

Thanks again.


Steve.

[Michael Alpert]

Steve,

The width and length of the exposed area will vary, depending on the focal length of the lens. Short focal length ("wide-angle") lenses will produce negatives that are noticeably larger than long lenses due to the angle of light striking the film at the edge of the image. I have never measured the difference, but I have noticed it in my 5x7 negatives.

I may be pointing out the obvious to you. If so, please accept my apology. I am not sure why you are asking for these dimensions or what your background in large-format photography is