Based on looking into the front of the lens from a distance, nearly the full 62mm diameter is active. This area estimation seems to give a consistent measure of the dedomed xpg2 luminance at 510Kcd at 4ish amps.
OSRAM SYNIOS® P2720, KW DMLQ33.SG White LEDs - ams-osram - ams
Learn more about the compact SYNIOS® P2720 KW DMLQ33.SG LED. Gives you flexiblity and full performance with just one footprint. Fore more information visit the product page.