70 x 56 mm image area · 1 interactive lens diagram
Pentax 67, Mamiya RB/RZ67, Mamiya 7, and Bronica GS systems | Nominal 70 x 56 mm film image area with an 89.6 mm diagonal
6x7 uses 120 or 220 roll film to make a large rectangular negative, roughly 70 x 56 mm in this taxonomy. Actual camera gates vary slightly, but the format's near-5:4 proportions are close to common print sizes, which helped make it popular for portrait, landscape, studio, and commercial work. Compared with 645, it gives a visibly larger negative at the cost of fewer exposures per roll and larger camera systems.
The optical requirements are substantial. A 6x7 lens has to cover nearly a 90 mm diagonal, so even moderate wide angles need generous image circles and careful off-axis correction. SLR systems such as Pentax 67 and Mamiya RB/RZ add mirror-box and body-depth constraints, while rangefinder systems such as Mamiya 7 can use different wide-angle layouts. Catalog entries in this format make those medium-format design choices easier to compare.