Making a spring back

[Michael Roberts]

What Tim said. The grooves hold a divider or splitter for making two images on one sheet of film. I've seen backs that hold both the 4x10 and a 5x8 divider simultaneously so that you could make four images on one 8x10 sheet.

[pgk]

I think it reduces the tendency to warp or change dimensions with changes in temperature or humidity??

Just had a look at mine and it looks to me as though it is part of a rebate to take a sliver of wood to joint it to another similarly rebated section of wood. This rebate appears only to be used at either end where it meets this other rebated piece of wood at 90 degrees. I'd say that the rebate was probably easier to cut along the whole piece of wood rather than try to machine just the two ends, so the empty rebate sits where it does no harm on the inside of the sprung back.

FWIW I found it far easier to fit a 5" x 4" back (Linhof) onto a ply back rather than attempt to build a new back myself. This also allows RFHs to be fitted.

[MadJake]

Don't you take the back off to change orientation? The fact that their is no wear in the groove may just mean it was never used to hold a blind; that the groove itself is a vestigial reminder of an earlier time when sliding backs were common in portrait studios and a groove for a sliding blind would allow shooting school portraits with two portraits on each sheet. For example, for a class of 32 you could take eight holders, shoot 16 portraits on the left side of the holders, open the back and shift the slide, then shoot 16 more on the right side.

A real sliding back allows you to shoot two portraits on the same sheet without changing the direction the camera points to, meaning the only adjustment needed for pupils sitting in a chair might be rise or fall, whereas using a screen would require you change the direction of the camera either left or right when you shift the screen. But a screen is a lot cheaper than a sliding back, so could be a cheaper alternative. To work with gravity, the groove on the top would need to be deeper than the one on the bottom so you could slide it up into the top groove, then drop it into the bottom. If the grooves are equal depth, you could still use something sprung in place. Or, I could be totally wrong!

I don't think it is to prevent warpage, as I'm pretty familiar with cabinetwork, and I've never heard of doing that, and also a back is held in place in all four corners, so not much chance to warp.

I now think its for a mask along the lines of what you have said Tim.

I also take your point regarding preventing warpage.

I'm not building a complete new back PGK, just the moving part, the GG screen holder. That way I can use the existing metal work.

[Tin Can]

I bought on this forum

I especially like my MINT Deardorff slider on my Deardoff matching Studio Portrait 8X10 with rear controls

[pgk]

I've also examined a 10" x 8" back too (I looked at the 5" x 4" previously)from Gandolfi and this has the slot but it does not extend the whole way across, just a bit from each end. So its not for a mask. I'm sure that its simply a part of the machining process to take the sliver of timber in the slot where it meets other timber.