Jadak PHOTO RESEARCH SpectraScan PR-655, Руководство пользователя

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PR-655/670 User Manual
76
U
SING THE
RS-3
OR
SRS-3 R
EFLECTANCE
S
TANDARD
The RS-3 Reflectance Standard has an absolute reflectance of 99% (± 1%) from 370 to 780 nanometers. Focusing
the PR-655 or PR-670 on the plaque allows the resultant luminance reading, in footlamberts (or candelas,
meter²), to be converted directly into illuminance values, in footcandles (or lux). It can also be used to establish
the 100% level for relative reflectance of materials or to measure the
Source part of an L*a*b* test of
Illuminated samples.
The technique is based on the definition that in the English System, the luminance (in footlamberts) of a perfect
Lambertian-diffusing surface is mathematically equal to the illuminance in footcandles which falls on its surface.
In metric SI units, illuminance in lux, equals

(3.1416) * luminance (in cd/m²).
2
/ * m cd lux

=
This method of measuring illuminance/chrominance is most convenient when physical conditions necessitate
remote source measurement, such as ambient light falling on a display surface. Since the illuminance
measurement is made in the plane of the RS-3 plaque, the measuring instrument does not need to measure the
source directly.
Never touch the surface of the plaque. Any surface damage or discoloration will result in erroneous
readings. Always keep the plaque cover closed when not in use.
Refer to the Cleaning and Handling Instructions for the RS-3 (and SRS-3) at the end of this section.
M
EASURING
P
ROCEDURE
The procedure for making illuminance/chrominance, irradiance and reflectance measurements with the RS-3
plaque are as follows:
Remove the protective cover from the reflectance standard and set it in the plane in which it is desired to
measure the illuminance/ chrominance, irradiance or reflectance.
1. For direct single source measurements place the RS-3 in the measurement plane. Arrange the
instrument so that it is oriented at approximately 45

to the white surface of the plaque, and is
sufficiently close so the measuring aperture is smaller than the image of the light falling on the plaque as
seen in the viewfinder.
OR
2b) For display surface ambient light measurements, hold the RS-3 plaque against the display screen in the
area to be measured.
2. Arrange the PR-655/670 so it is oriented perpendicular to the white surface of the plaque (or at the
required angle for the display under test), and is sufficiently close so that the measuring aperture is
smaller than the image of the light falling on the plaque as seen in the viewfinder.
3. Hold the PR-655/670 securely by hand or place it on a sturdy tripod or other suitable support.