ISO 686:1985

Photography — 35 mm filmstrips — Specifications for double-frame and single-frame formats

Establishes a parity of aspect ratios between the double-frame and single-frame formats from the same artwork or master material. To facilitate the production of filmstrips from a series of slides, the dimensions of the double-frame format have been selected as the mask aperture size of the nominal 24 mm by 36 mm picture area.