Mystery Plate Size?

[Steve S]

I came across this plate holder in the market today and had to buy it as it supports a size I have nevwe come across. It would seem to hold a glass plate 3 1/8 inches by 3 1/4 inches approx (182mm x 184mm). I am wondering if any one has come across this size and if so any idea which cameras employed it

 

[railwayman3]

I can't find any reference (in any of the old photo books which I have) to this being a standard plate/film size for general photography. Could it be a special size for a scientific instrument, maybe a microscope or telescope producing a circular image?

 

[Ian Grant]

Is it a Lantern plate holder, Autochromes (and some early competitor films) where sold in Lantern plate sizes for projection - they were reversal process.

Ian

 

[Steve S]

Ian, I really thought you had the answer there for a moment and perhaps you still have if there was a variation in the standard for lantern slides. I have tried to fit a few in and they are too large by about 2 mil. on the shorter dimension. It does seem like the most likely answer but I'm really hazy regarding the process whereby lantern plates were created. If they used their own plate holders were they used in some sort of reducing back on a standard quarter plate or half plate camera do you think?

 

[Ian Grant]

Steve. I'll check later in my BJP Almanacs and I also have some lantern slides and Ilford Lantern slide boxes, meanwhile I'm off to see some experts at a camera fair so will ask there for you. It's possible it's a Continental size.

Ian