The Seagull 4B SA-85 is a twin-lens reflex camera produced by the Shanghai Camera Factory, shooting 6x6cm frames on 120 roll film. It follows the classic Tlr design established by Rolleiflex, offering a waist-level shooting experience in a self-contained, non-modular body. The Tlr configuration uses two lenses of identical focal length — one for viewing and composing on the ground glass, and one for exposing the film. This arrangement eliminates viewfinder parallax at typical shooting distances and produces no blackout during exposure, unlike SLR designs. The 6x6cm square negative eliminates the need to decide between landscape and portrait orientation at the time of shooting. It delivers significantly greater detail and tonal range than 35mm, with a square composition that suits a wide.