Hi guys,
If I want to make an LED flash for taking a photo, similar in its power to a flash of a modern phone... what kind of a led should I be looking for and could I connect it directly to arduino or should I make some circuit with a capacitor?
Thanks )
Ultrabright white LEDs with 18000mcd of output at 20mA are directly drivable from Arduino - and blindingly bright.
And look at this one - not even measured on mcd, but cd!
http://www.mpja.com/8mm-White-100000mcd-LED/productinfo/30029%20OP/
Probably drive with a transistor from 5V tho, not an output pin.
Gonna need a diffuser for sure with these puppies.
The other thing to check is the color output:
6000-6500K White vs unstated - some might seem too cold & clinical.
Probably want to read some reviews of color to use for best results.
You can see the ranges of white available here
http://www.superbrightleds.com/cat/component-leds/
Cool White, Natural White, Warm White, White, Variable White.
Thanks for the info, I've found "5mm clear white 25cd 15gr" in my local store. Not sure about their mA, thought. Do you think connecting like 4 of them in a chain and to an output pin would be fine? 
Probably not - 4 in parallel would be too much current for an arduino pin directly. 4 in series would need a higher voltage to drive them.
ok, then with a transistor for the USB ? )
Sure, that'd work.