LEDs are not lasers.
“Thank you Captain Obvious,” you say.
Yes, well, let’s be a bit more specific: LEDs are different than lasers in two distinct ways: broadband wavelengths (in the case of white LEDs) and high divergence.
However, when we throw in high power (tens of watts or higher), there’s really only one way to measure the LEDs: broadband-coated thermal sensors.
And when it comes to thermal sensors, the best coating for measuring broadband, divergent beams is LP2, hands down.
You can see this quite clearly from the graphs of LP2 compared with LP1, its predecessor: