The FAST checklist uses the incorrect term "luminosity". This is a common mistake, but is incorrect. The correct term (and the one used in WCAG) is "luminance".
Wikipedia has an accurate definition of luminosity, which is a term used in astronomy:
In SI units, luminosity is measured in joules per second, or watts. In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, L⊙.
Notice that this is total electromagnetic energy, unrelated to whether that is visible light or some other energy (infrared, ultraviolet, etc) and unrelated to human perception.
The Wikipedia definition of luminance is okay, but hides the relevant difference away under luminous intensity:
The crucial point here is that the value is weighted for human perception, so green and yellow light makes more contribution than orange, red, blue, and violet.
I suspect that the confusion comes from the term luminosity function in the definition? But the luminosity function is a graph of (human perceived) brightness vs. visible wavelength, and unrelated to the astronomical definition.
Anyway, please change
Luminosity and hue contrast can adapt to user requirements.
to
Luminance and hue contrast can adapt to user requirements.
The FAST checklist uses the incorrect term "luminosity". This is a common mistake, but is incorrect. The correct term (and the one used in WCAG) is "luminance".
Wikipedia has an accurate definition of luminosity, which is a term used in astronomy:
Notice that this is total electromagnetic energy, unrelated to whether that is visible light or some other energy (infrared, ultraviolet, etc) and unrelated to human perception.
The Wikipedia definition of luminance is okay, but hides the relevant difference away under luminous intensity:
The crucial point here is that the value is weighted for human perception, so green and yellow light makes more contribution than orange, red, blue, and violet.
I suspect that the confusion comes from the term luminosity function in the definition? But the luminosity function is a graph of (human perceived) brightness vs. visible wavelength, and unrelated to the astronomical definition.
Anyway, please change
to
and also change
to
Notice that WCAG 2.0 and 2.1 both use the correct term, luminance: