Translation guide
How to express 'brightness' in Japanese, covering light intensity, vividness of color, intelligence, and mood.
The amount of light emitted or reflected; how bright a light source or surface is.
The most common and general word for brightness of light, a room, a screen, etc.
画面の明るさを調整してください。
Please adjust the brightness of the screen.
この部屋の明るさはちょうどいい。
The brightness of this room is just right.
Technical term for luminance or brightness, used in physics, displays, and photography.
このモニターは輝度が高い。
This monitor has high brightness.
Luminous intensity, a scientific measure of brightness from a source. Rare in daily conversation.
光源の光度を測定する。
Measure the luminous intensity of the light source.
How bright or vivid a color is; saturation or intensity.
Refers to vividness or brilliance of colors. Commonly used for clothes, paintings, nature.
この絵の具の鮮やかさが好きだ。
I like the brightness (vividness) of this paint.
花の鮮やかさに驚いた。
I was amazed by the brightness of the flowers.
Can also be used for color brightness, but less specific than 鮮やかさ. Often implies lightness rather than saturation.
色の明るさを変える。
Change the brightness of the color.
Referring to a person's smartness or quick-wittedness.
Intelligence, wisdom, cleverness. Often used for people or animals.
彼の賢さには感心する。
I'm impressed by his brightness (intelligence).
Literally 'goodness of head', a common way to say intelligence or brightness.
彼女は頭の良さで知られている。
She is known for her brightness (intelligence).
Smartness, often used for children. Somewhat formal or literary.
その子の利発さに驚いた。
I was surprised by the child's brightness.
A positive, cheerful mood or atmosphere; optimism.
Also used metaphorically for a cheerful personality or bright atmosphere.
彼女の明るさに救われる。
I am saved by her brightness (cheerfulness).
職場の明るさが足りない。
The workplace lacks brightness (cheerfulness).
Cheerfulness, liveliness, often describing a person's disposition or atmosphere.
彼の陽気さが周りを明るくする。
His brightness (cheerfulness) lights up the surroundings.
明るさ is the everyday word for brightness. 輝度 is technical for luminance (cd/m²). 光度 is luminous intensity (candela). Use 明るさ unless you are in a scientific or technical context.
Do not use 明るさ to mean intelligence. It sounds unnatural. Use 賢さ or 頭の良さ instead.