4.5×6 cm film format; semi-Brownie format
Photography term for a medium-format film size, historically associated with the 'semi' (half) Brownie cameras. Used in technical and vintage camera contexts.
This old camera uses 4.5×6 cm film.
I scanned the semi-format negatives and digitized them.
From English 'semi' (half) + 判 (size/format), referring to the half-size version of the Brownie film format.