These two websites: http://www.increa.com/reverse/dc/ and http://thesignalpath.com/blogs/2011/06/12/camera-flash-circuit-and-nixie-tube-tutorial/ have very similar circuits for a standard camera flash circuit...and overall do a decent job explaining them. There is one question I have though......one thing they do not explain in detail and I'm not quite sure what the answer is. The question is WHY the transistor ever shuts off? WHY does it go into the cutoff mode for a short period of time? What is causing this? So........what causes the transistor to go into cutoff? Does anyone have a good (detailed) explanation? Thanks!