Do you know what we can use to measure light output from a flashing xenon lamp?
It flashes once per second, -the current flow associated with the flash only lasts for about 200us, (but obviously the eye sees the flash for longer than this)
Why do you need to do this, measuring light output is complicated, can't you rely on the manufacturers data? if you are just need to do some comparison, set up your own jig - Photo cell and flash tube (in a holder) inside a cardboard box painted black inside.
Frank