FP is a cubic-grain[2] black-and-white film from Ilford Photo with a long history.

[3] It originated as Fine grain Panchromatic roll film in 1935.

Like its faster partner product, HP film, it has gone through a number of versions since then, with the latest being FP4 plus (FP4+ for short).

[1] This is due to the fact that FP4 features a double layer emulsion.

Being perfect for the amateur's 6x9 roll film cameras these old types lacked sharpness in the 24 x 36 mm format due to the overall thickness of both layers.