Re: adding a 7x11 expansion back to an 8x10
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'.).
Re: adding a 7x11 expansion back to an 8x10
2" spacer back under construction...I used 1/2" x 1/8" and 1/4" x 1/8" basswood strips for the rabbets/lighttraps...
Re: adding a 7x11 expansion back to an 8x10
finish...came out a little darker than the camera, but what the heck, it's an after-market add-on accessory....