Caption: A schematic diagram of psychophysical sensitivity of the average human eye (i.e., luminosity function).

Features:

1. The horizontal axis is wavelength in nanometers (nm).

2. The visible light band has fiducial range 0.4--0.7 μm (400--700 nm)---i.e., the range everyone remembers to say.

3. The vertical axis is actually luminous flux per unit power.

   Luminous flux is the quantity of psychophysical sensitivity of the human eye with units lumens.

   Power has units of watts.

4. There are actually two luminosity functions.
   1. Photopic vision: the luminosity function under well lit conditions.
   2. Scotopic vision: luminosity function vision under poorly lit conditions.

   Scotopic vision is rather insensitive to color---it's nearly black-and-white vision.

5. For more on vision and color vision, see the Vision videos below (local link / general link: vision_videos.html):

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6. For seeing beyond the visible band (fiducial range 0.4--0.7 μm), see the insert visible_band_extreme.html below (local link / general link: visible_band_extreme.html):

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