- Spectral power distribution of coloured LEDs. The Royal blue tends to go towards the purple colour.
What flux value to choose for royal blue?Download the PDF
Royal blue is a very deep blue. Usually, LEC gives values in watts rather than lumens, because in this lightwave range:
- human eye perception is decreases considerably acco,
- the value expressed in lumen is low,
- daytime and night-time vision are not the same.
Note: As photopic (daytime) and scotopic (night-time) vision are different, lumen values vary depending on the ambient light.
For example, here are two LED wavelengths for a flow of 489 mW.
Daytime luminous flow
- at 455 nm = 16.3 lm
- at 460 nm = 20 lm
Night-time luminous flow
- at 455 nm = 425 lm
- at 460 nm = 471 lm
Two measures of light energy
Watts and lumens are two ways of describing the same thing, only using different units.
- Watt (W) characterizes the universal and absolute size of electrical power. This value corresponds to the energy flow.
- Lumen (lm) is the size used in the world of lighting technology. This value takes into account eye response, and corresponds to the visual flow.
Thus, a watt in green and a watt in blue do not give the same response in terms of lumens. There are many more lumens in green, than in blue where the eye is not very sensitive.