"Candelas Lumens and Lux" introduction to lighting  terms and calculations
"Candelas Lumens and Lux" introduction to lighting  terms and calculations




What is luminance?

Luminance is apparent brightness, how bright an object appears to the human eye. So when you look at the world what you see is a pattern of varying luminances (if we ignore the color component). What you see on the this page you are reading is the luminance of the black letters compared to the luminance of the white screen.

Luminance is measured in candelas per square meter.

Since luminance is what we see then light sources which we look at have luminance too. The luminance of the sun and the moon give us a good idea of the huge range of brightness which the human eye can handle.

Luminance of the sun: 1,600,000,000 cd/m2

Luminance of the moon: 2500 cd/m2

If you look at the sun you'll get 1,600 million candles per square meter into you eye. That is why you should not look directly at the sun for very long.

In the diagram below (taken from the chapter on Luminance my book "Candelas Lumens and Lux") a light source illuminates a piece of paper, but your eye percieves the luminance.

Luminance is what gets into your eye

Glare is very closely related to luminance, and is explained in a whole chapter in Candelas Lumens and Lux:

"Candelas Lumens and Lux" book cover


Here is the poster of the book, ideal for school, colleges and universities:

Poster of the book

Click here to buy the poster from Zazzle for $16.80.
The poster is 28" by 20" (71 x 51cm)

See also Sollner and UGR. For road lighting the UNI 13201 2 standard is sometimes used.


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