Brightness and Luminance
In the preceding chapter we have already used the notion “brightness”. Until now it has remained a more or less vague concept indicating the amount of light striking the eye of the observer. In the International Lighting Vocabulary, the C.I.E. gives the following definition for brightness or luminosity: “The attribute of visual sensation according to which an area appears to emit more or less light”. We shall in future use the word “brightness” in this sense, and the word lightness in the sense of § 5 where “brightness” applies to a colour in relation to its surroundings. The difficulties following from the subjective character of the notion brightness prompted Schrödinher 2 in 1920 to suggest developing the theory of colour without making use of a concept of this kind. He showed this to be possible. From a theoretical point of view this course seems very attractive; however, in practice the connection between colorimetry and photometry is so close that such a separation is not to be recommended.
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