Can someone tell me the difference between the 545 and 550 backs? I can't seem to find anything that explains the difference. Is one just a newer version of the same model?
545 - Uses individual 4x5 polaroid sheets - still being made, easy to find
550 - Uses pack 4x5 polaroid - holder is discontinued... Can you still get polaroid for it?
If you are looking for a polaroid pack film holder, look into the 405 back... I have one and while it does shoot a smaller image, it's great for exposure checking. My suggestion is the 545 or 405.
I believe that although the 550 back fit 4X5 cameras it actually gave a 3 1/4 x 4 1/4 image. Same film used in all the pack film cameras. If you can find one, it's a lot less expensive to shoot.