Lumidisc - Sekonic L-398M Operating Instructions Manual

2. Lumidisc.

Employ for illumination contrast
Adjustment and luminance measurement.
• Contrast measurement
a. Mount Lumidisc
sensor
Install in the same
manner as Lumisphere.
b. Hold meter at subject position
and point Lumidisc
directly toward center of main light.
c. Press stopper button
read meter scale footcandle
indication
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
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
footcandles, fill-in light reads
320 footcandles.
contrast ratio becomes:
640
320
11
between the
(=
light at 640
Illumination
2
1 or 2 : 1