I was trying to make the distinction between "high brightness" and "high power" LED's. High power LED are certainly highly bright, but high brightness LED's are not necessarily high power.
I agree with the lack of necessity of the opto, but I would parallel 2 series LED's with 300 ohm resistors and not put the 4 LED's in series, not enough headroom for good current regulation, especially if run on batteries.
this started out as a simple go no go tester for optos.....mainly used when iv had an smps which either isnt working or working but no regulation(depending on design)...was built fairly quickley using parts i had to hand and is here for anyone to have a play with and change however they wish.....the leds were actualli obtained from the £1 shop ....they sell 6 lighters at a time with hi brightness leds in them which were used on this and the flash is quite bright using these.
yes u could use a 555 but i had none to hand and building a 2 transistor osc with the components i had to hand worked fairly well and it was made reasonably small too.its already proved itself opto wise for testing...