35 mm Format
The film format using 35 mm perforated stock with a 36 by 24 millimetre frame, which became the dominant standard of the twentieth century.
Measured in
mm
In depth
Barnack adapted cine film for still use, running it horizontally to double the frame area, and in doing so created the format that made handheld reportage possible. Its dimensions still define the vocabulary of photography: focal lengths, depth of field expectations and the 3:2 aspect ratio all descend from that choice.
Examples in practice
A standard 36-exposure cassette of 35 mm film gave photojournalists a whole assignment's worth of frames in a pocket.