Abstract

The CIE definition of luminance requires a standard luminous efficiency function V lambda. There are in fact three CIE standard luminous efficiency functions: the CIE 2 and 10° photopic functions and the CIE scotopic function. Visual scientists frequently need to measure the amount of light with reference to their observer’s spectral sensitivity. Heterochromatic flicker photometry is the most frequently used method. When light measures are a function of an individual observer's spectral sensitivity function, visual scientists use the word luminance. Using this expression for both the standard CIE function and individual observer function can be an annoying source of confusion. This paper discusses how we can emulate auditory science where a similar potential confusion is avoided by distinguishing between sound pressure level and sensation level. When luminance measures are based on an individual's spectral sensitivity they could be referred to as sensation luminance or s-luminance for short. Visual scientists distinguish between luminance and retinal illuminance; the unit of measurement for the latter is the troland. I propose that the unit of measurement for s-luminance be the ives in honor of Herbert E. Ives who did the pioneering work in heterochromatic flicker photometry.

© 1987 Optical Society of America