brightness
Luma (video)
Luminance (relative)
Luminosity
https://source.unsplash.com/featured/?brightness#.png
/suto3/google.iconbrightness
/suto3/Google画像検索.iconbrightness
/suto3/Google定義検索.icon brightness
/suto3/wikipedia.iconbrightness
/suto3/weblio.icon brightness
/suto3/kotobank.icon brightness
/suto3/jisho.icon brightness