Luminance
Brightness
noun
The radiance degrees show the luminance and brightness of something.
This is a technical term used in physics. It refers to the amount of light reflected or emitted from a surface.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
例えば、太陽の輝度値はとても高いです。
For example, the sun’s luminosity value is very high.