Full Frame
A sensor the same size as a 35 mm film negative, 36 by 24 millimetres, treated as the reference format for focal length and depth of field.
Formula / rule
Crop factor = 1.0
Measured in
mm
In depth
Full frame is a reference point rather than an inherently correct size — it exists because Oskar Barnack chose to run cine film sideways in 1913. Its persistence means every focal length conversation defaults to it, and its area gives roughly a stop more light-gathering than APS-C and two more than Micro Four Thirds at equivalent framing.
Examples in practice
A 50 mm lens on full frame gives the classic natural perspective the format's whole vocabulary is built around.