View Full Version : adding a 7x11 expansion back to an 8x10

Michael Roberts
24-May-2010, 15:02
In my 8x10 kit I carry a 4x5 reducing back and wooden splitters that fit inside the 8x10 spring backs on my Kodak 2D and Century Universal that permit 4x10 and 5x8 formats. I love the versatility this gives me--four formats with one camera. Recently, I decided to try to add a fifth format--7x11. I purchased a vintage 7x11 back from Jim Galli that I thought would be a good, vintage match for my older cameras. I knew the 7x11 back would need to be modified. I wasn't sure how much of an extension I would need to avoid vignetting, but I thought it was doable. Thinking that somebody else might be interested in trying this, I am posting to share my experiences in adding a 7x11 back.

When the back arrived from Jim, I was delighted to measure the depth and discover it was over an inch thick. It was also 11 and 7/8 inches square (o/s), and my camera backs are 11 and 1/2. I took the back to a woodworker who has helped me with vintage camera mods in the past and had him trim the top and bottom to 11 and 1/2 (I decided to forgo portrait mode for the time being). I went back a second time and had him trim out the inside to a true 7" x 11" since the original opening was quite a bit smaller (about 1/4" each way).

To make the back usable without adding a cumbersome 2-3" thick spacer, I filled in the rabbet and added a new light trap myself. Pictures below.

W/o any additional spacer, the back is usable with 2-3 lenses: a 159 ExWA Wolly, a 210mm Fuji (these two do not vignette even when wide open), and I think I can use it with a 300mm when stopped down (need to verify this last).

First pic below shows the back w/o gg after trimming. Second shows detail of the top/bottom cut. Third shows detail of the inside opening.

Michael Roberts
24-May-2010, 15:09
1/8 x 1/8 basswood trim to fill in the rabbet...

Michael Roberts
24-May-2010, 15:11
with the 7x11 back on the camera, w/o gg, you can see the potential for vignetting with the bellows frame.... Second pic shows an angled view to the side/corner...

Michael Roberts
24-May-2010, 15:15
these show how the new back lines up with the existing corner brackets. I thought it would be dicey drilling holes for the new pin placement, but it turned out not to be a problem....

Michael Roberts
24-May-2010, 15:17
these show the new light trap added to the back. 3/16 basswood.

Michael Roberts
24-May-2010, 15:19
new 7x11 back on 8x10 camera

Michael Roberts
24-May-2010, 15:22
I'm working on a 2" thick spacer to use for longer lenses. I'll post pics of it in a day or so. The 2" spacer will also make it easy to reverse the back for portrait orientation.

If you are interested in this, eddie currently has a 7x11 back for sale (and about 20% less than I paid for mine, so it's a good deal).

24-May-2010, 16:53
Were the backs modified to accept the splitters, or were the notches (like a Deardorff?) already there? Also, are the backs interchangeable? I'm waiting for a Century Universal to arrive any day now...
It would be nice to see 7x11 capabilities on it one day.

Michael Roberts
24-May-2010, 17:15
My 2D and CU backs were originally made to accept wooden splitters. The have brass inserts, apparently with some sort of spring inside the slots as well. The splitters have a longer and a shorter edge--push in the longer edge, then fit in the shorter one and wiggle a bit to adjust into place. Yes, my two backs are interchangeable. The CU and 2D were in production at the same time, so apparently the Folmer Graflex Division/Folmer-Schwing folks took interchangeability into account--or they just used the same parts and designs for both backs.

My 2D is a late model--'48, I think. The CU is around 1935. I don't know if FG/F-S or Deardorff came up with the grooved back splitter design first. Maybe somebody else knows....

24-May-2010, 17:46
I'm not sure who came up with it first, but it sounds like the grooved back is similar to the Deardorff back splitters. I've owned a couple of Deardorffs, and several backs. Not all of the 8x10 'dorf backs have the groove/notch.

Michael Roberts
21-Nov-2010, 15:56
Six months later....I finally finished the 2" spacer back. With the spacer back, no vignetting on 7x11 with a 450mm or 24 inch (610mm) lens (haven't tried the 30 inch yet). Without the spacer back, no vignetting on 7x11 with 300mm and shorter lenses.

I made the spacer back out of 2" x 1/2" balsa wood and covered it with 1/16" inch basswood. Weighs 1/2 pound.

Two bonuses--with the spacer back I can: (1) reverse the 7x11 back to portrait orientation, and (2) I gain 2" of extra "bellows;" the latter will come in handy when using the 30" lens even with 8x10 or the 4x5 reducing back (I ran out of bellows a few months back trying to photograph petroglyphs with the 30" lens and 4x5 reducing back across a roped off area--not enough bellows to focus the 30" lens at 20'.).

Michael Roberts
21-Nov-2010, 16:10
2" spacer back under construction...I used 1/2" x 1/8" and 1/4" x 1/8" basswood strips for the rabbets/lighttraps...

Michael Roberts
21-Nov-2010, 16:11
finish...came out a little darker than the camera, but what the heck, it's an after-market add-on accessory....