The scales on the Weston Masters till NR IV are given in cd/ft2. Thus primarly designed to measure LUMINANCE! From the Weston Master V and on the scales just have arbitrary numbers... The scales read in the low light with open baffle from .2 - 50 and with the baffle closed (High light) from 25 - 1600. Hence note the overlap of the numbers 25 and 50 on both scales to facilitate proper switching between high and low.(Also in a lesser degree to overcome the discrepancies from the galvanometer movement (which is not linear).

LUMINANCE, BRIGHTNESS Luminance (brightness) in a given direction = luminous intensity emitted per unit area per steradian of solid angle of the receiver = candles/cm² Lambert = brightness of a perfectly diffused surface emitting or scattering 1 lumen/cm² = 10-4 lux. candles/cm² = Lambert candles/m² = meter-Lambert candles/ft² = foot-Lambert Note: if measuring device's field of view is filled, distance from source to measuring device is irrelevant.

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