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Illumination ratio can be
varied by keeping the main
light fixed and varying the fill
in light.
Reflected Light Measurement
Reflected light measurement is employed for the following purposes.
a. Luminance range adjustment.
b. Self-lighted subjects such as neon signs which can only be measured by reflected light
method and locations such as show windows where meter cannot be brought into proximity
with subject to allow incident light method.
Measurement in these type situations in described below.
1. Luminance range center point
Refers to measuring subject luminance by reflected light method. This luminance varies
somewhat according to incident light strength and surface reflectivity of the subject.
Incident light becomes measured by taking the standard surface reflection as 18%, from
which the exposure value is determined.
To obtain accurate exposures, the Lumisphere is used to measure effective footcandles to
determine the Luminance center point.
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