• What flux value to choose for royal blue?
Lighting techniques

What flux value to choose for royal blue?

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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.

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