I was planning to take a fake multiple-exposure picture: use a dark room, long exposure time, and manually trigger a flash for each exposure. But can I trigger my Canon Speedlite 430EX II manually without any extra gear?
This would be trivial if I had two camera bodies, but no such luck.
Of course there is the test button in the Speedlite unit. But exactly what does the test button do? How much flash power do I get this way; can it be adjusted by using the manual mode? Is it just a tiny burst of light so that I can see that the unit is alive, or can I use the test button to get consistent exposures?