Fluence (Joules/cm2)
Quick definition
Fluence is the total dose of light energy your skin receives during a session.
The Science
Fluence is the simple math relationship between intensity and time. If irradiance tells you how strong the light is, fluence tells you how much energy your skin receives across the whole session.
Why it matters for your skin
A weak mask can still deliver a useful fluence, but only if the session runs long enough. This is why session length matters so much in at-home LED devices.