43.8 x 32.9 mm image area · 16 interactive lens diagrams
Fujifilm GFX, Hasselblad X, and related digital medium-format systems | 43.8 x 32.9 mm sensor with a 54.78 mm diagonal
The 44 x 33 mm digital medium-format class is a practical compromise between full-frame portability and larger medium-format capture. It offers about 1.7 times the image area of 35 mm full-frame while staying well below the usable frame of 645 roll film. That difference matters: these systems are marketed as medium format, but their image circle requirements are closer to a modern digital standard than to the largest traditional film gates.
The format's 4:3-ish shape and 54.78 mm diagonal give lenses a wider field to cover than full-frame, while mirrorless camera bodies avoid the deep mirror box of medium-format SLRs. Designers still have to satisfy very high-resolution sensors, so field uniformity, chromatic correction, vignetting control, and mechanical precision matter across a large image circle. In the catalog, 44 x 33 designs are useful for comparing how mirrorless lens layouts scale when the image circle grows beyond full-frame without reaching full 645 film coverage.