2. Lumidisc. Employ for illumination contrast
Adjustment and luminance measurement.
b. Hold meter at subject position
and point Lumidisc
directly toward center of main light.
read meter scale footcandle
d. Turn the memo pointer dial and set the
pointer 1 7 at the footcandle value the
needle points to
e. In the same manner, measure the fill-in
light. In this case, use care that light from
main source dose not enter sensor.
f. Read a difference between the
footcandle value the pointer is set (see
above c) and the one for fill-in light (=
needle position.
Ratio between main and fillip light
footcandles becomes the contrast ratio.
Example: With main light at 640
footcandles, fill-in light reads
320 footcandles. Illumination
contrast ratio becomes:
640 2
320 1 or 2 : 1
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