Sinar DB/DBM Auto Aperture Cable + Bayonet (521.51). Condition: EXC.

The Sinar automatic aperture cable, part 521.51, supplied here with its 521.91 bayonet piece - the pair of parts that bring a Sinar DB or DBM auto-aperture shutter to life. This is not a shutter release and has no plunger. It is the mechanical interlock link: one end connects to the DB shutter, the other to the camera's rear standard by way of the bayonet piece. With the cable fitted, inserting a film holder automatically cocks the shutter and closes the lens down from full aperture to the working aperture you have set, so you focus and compose wide open, then shoot stopped down without touching the lens. Take the cable away and the whole automatic function is lost, which is why so many DB shutters turn up on the used market unable to do the one thing they were bought for. Approximately 93cm long in a metal armoured sheath, with the original bright metal fittings at both ends. These are scarce; the cables were easily separated from their shutters over the years and rarely come up on their own.