7P
From Photo-3d
7P is a 3D film formats and the name stands for seven perforations (also known as perfs) of 35mm film. This style is also known as "European Format". The image area is typically 24mm x 30mm.
This pattern requires the camera to advance first one frame, then three frames - the extended sequence on film is 1L2L1R2R - 3L4L3R4R - 5L6L5R6R - etc. (i.e. there is one frame between the lenses)
