B&J 5x7 > 8x10 "step up" Back, Anybody Know Anything About This?

I recently purchased a B&J 5x7 camera that came with several backs, one which seemed to be the most used was an 8x10 "step up". I have tried searching around to find some info on this but no luck so I am wondering if anybody here knows anything about such a beast. This 8x10 back looks like the previous owner used it the most (GG is rubbed raw), it was used in studio only and was in very good condition.

Here are a few photos showing the back installed on the camera and also compared to the 5x7 back it came with. The GG has the Burke & James name etched in the lower corner but no markings on the actual wood...but neither does any other wood component of the camera. The final image size exposed on the negative is about 7-3/4" x 8-1/4"

Any info would be much appreciated...TIA!

8x10 compared to the 5x7 back



you can see the "step up" boxed part of the 8x10 back in this photo


on the camera you can easily see the step up size




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what? wouldnt this cause massive vignetting? Is it because of the availability of 5x7 film these days?

Looks like a homemade job to me. Why the crafter didn't make it go full 8x10 format is curious because it appears there is enough rise on both the front and rear to keep the adapter from interfering with the bed.

Tachihara made such expansion backs as did Rittreck (pre-Wista). There are usually a few Rittreck 5x7 to whole-plate or 8x10 expansion backs listed everyday on ebay. I have two of the whole-plate expansion backs along with 15 mating film holders and am in the process of refurbing a 5x7 Rittreck body. (The Rittreck WP holders are dimensioned differently than older manufactured ones from ROC, Eastman, Toyo, Premo, etc., and are not interchangeable.) I also have a Toyo half-plate to whole-plate expansion adapter but that incorporates a bellows and mates underneath the camera bed as well as on the back of the earliest metal half-plate field camera they manufactured. (I'm currently looking to purchase the front end of that arrangement so if anyone has that camera for sale, please contact me.)

So, expansion backs are around but are unusual. I've also seen an 8x10 to 11x14 back for a B&J many years ago. If the additional expansion/extension is long enough, there shouldn't be a problem with vignetting. The GG just has to be back far enough to form a line with the lens and corners of the normal format back. However, that will add weight and bulk, and these backs do limit movements and become awkward depending on their size and design.

Ahh....Expansion Back...I like that name much better....well if it is home made it is darn good and matches almost exactly everything else with the camera, it has the same finish and color as all of the other backs and components of the camera. There is no vignetting at all, here is a whole scan of Fuji HR-T I made with it:



Thanks for the info!

I have one for my Rittreck 5x7. no vignetting. you are restrained with the movements as ilustrated further above. but it's a nice extension for an existing system.