Do bear in mind that this will have the fraction of the power of a regular camera flash.
50 of those white LEDs have a combined input power of about 3.5W (not including resistor losses). A typical camera flash has an input of around 45w per flash. I think you'll find that while quite bright, those LEDs would not light a room to the same degree, or to the same effect (LEDs are much more directional), as a xenon flash.
Also note that magnatro's schematic shows the LEDs wired in series - you would need to wire them in parallel.
Also for the LEDs you have chosen, you will need a 12v supply.
- Pin 4 of the second 555 must be high for it to work - the best way to do this is connect it straight to pin 3 of the first, then connect pin 8 of the second to V+. With pin4 floating, the circuit won't work.
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Andrew