Take a look:
What do you think? Of course I know that this can't be absolutly correct measurement. But it gives me a value for comparison.
Here are some measured values in mV:
Nuwai Q3 295
Fenix L1P 2.5 291
GlooTob FX Blue
Arc-AAA Premium (2005) 266
NoName 3W 3xAAA 313
What do you think about these measurements? Are they correct? They seem to be logarithmic. I'll have to look for the charactieristic curve of that photo diode I used.