| Definition: | unit used to express a quantity proportional to retinal illuminance produced by a light stimulus. When the eye is viewing a surface of uniform luminance, the number of trolands is equal to the product of area in square milimetres of the limiting pupil, natural or artificial, by the luminance of the surface in candelas per square metre
NOTE 1 – In computing effective retinal illuminance, absorption, scattering, and reflection losses and the dimensions of the particular eye under consideration must be taken into account as well as the Stiles-Crawford effect.
NOTE 2 – In German, "Pupillenlichtstärke" designates the retinal illuminance.
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