justapax - semtex won't go off from a spark in your camera. It won't even ignite. It won't explode if you set fire to it with a match or put it in a fire. It will just burn. Most (probably all) modern plastic explosives behave this way.
Semtex requires a detonator of some kind (e.g. a blasting cap, shotgun shell, detonating cord,...) to get it to actually explode.
Strangely enough, gunpowder although only a low explosive, is more hazardous to handle than semtex or modern smokeless firearm propellants as a static spark CAN set it off. It won't explode (unless confined), but it burns EXTREMELY rapidly, much more so than semtex or nitrocellulose. I enjoy demonstrating this!
Mik
(muzzle-loading firearms instructor)
[This message has been edited by mik (edited 07 July 2000).]