AlienBees: Illuminating the Galaxy with Professional Photographic Lighting Equipment. PN Peanut Slave (100' Range) The Flash Centre - Home Page. Canon Speedlite 550EX as a dumb optical slave - Open Photography Forums. We often have questions about using the Speedlite 550EX flash unit as a "dumb slave", optically triggered by, for example, a studio flash system.
A common motivation is to use it as a background light or hair light. If we try to do this with a widely-owned optical slave trigger unit, the basic Wein hot shoe type (type HS), we find it won't work. The 550EX is fired by the first burst from the studio lights, but then the system "locks up", and subsequent bursts will not fire the 550EX. PocketWizard® - Remote flash and camera triggers for professional and advanced amateur photographers. Strobist.