Instant film backs for 9x12 cm plate cameras

I have just recently discovered the joy of using instant film with a 6x6 medium format camera, and it occurred to me that the 3"x4" instant film packs might be used with a 9x12 cm plate camera (I have collected a few, mostly from the early 20th Century) Thus far, I have been unable to locate a film back specifically for these size cameras, so I was wondering if anyone has heard of such a product, and, if so, where I might obtain one. I'm sure its possible for me to modify another back for such a purpose, but I lack the necessary knowledge and skill to do so on my own. I'd appreciate any information I can get concerning this matter. Thanks.

Hello:

I have no direct experience to contribute but I expect that conversions for 4x5 Polaroid 545 film backs would be possible or have been done. Anyone with experience to contribute?

'Best in the New Year to you.

yours
Frank

Depends to some extent on the camera. I've been looking at my Ziess-Ikon Ideal 250/7 with the idea of making a 4x5 spring back or Graflok converter that would go where the plate holders do, including enough setback to avoid significant vignetting; this would then allow use of 405 and 500/545 Polaroid backs made for 4x5 cameras. I'd probably have to find a 150 mm lens to fit the existing shutters, since it would involve setting the focal plane back around a half inch (with care, I might be able to use the existing infinity stop with the slightly longer lens, but the focus scale would still be off; fortunately, this camera has a second scale pointer without a scale, which would nicely support an alternate scale for this setup).

And that's the major rub -- you're going to have to either reset the infinity stop, or replace the lens with a longer one and then either focus only on the ground glass, or make a new scale (or new RF cam if you're fortunate enough to have an RF-equipped plate camera). Still, might be worth doing if only for the ability to use readily available, light-tight modern film holders and the wider emulsion and processing choices for 4x5...