Well then, let's pulse!

Amazing how things can be "not as simple" as they would look like at a first glance.

If I understand you weel, the idea is to get rid of resistors and power the leds with an appropriate pulse (hope I'm right here).

About maximum "brightness", how do I measure it? I assume I'll have to use the led's datasheet specs for a value (mA)... but when pulsing power to the led, the time to measure the current will be far to slow for my ampmeter (Vf is not difficult to measaure with my oscillo but this value is not mentionned in the datasheet ).

Second, if the PWM doesn't allow frequencies lower than (can't recall exactly) around 250Hz, how would you do?

I'm not an expert in PWM so I may have missed some infos on how to go that low in freq.