Jadak PHOTO RESEARCH SpectraScan PR-655, Руководство пользователя

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PR-655/670 User Manual
74
For the PR-655 and PR-670, the (optional) accessories used to measure illuminance are the
CR-655 or CR-670, and the RS-3 or SRS-3. The CR-655 (or CR-670) is a diffuser that serves as the surface upon
which the incident light falls. During calibration these accessories are photometrically calibrated using a
standard lamp whose candela rating has been certified to NIST standards. By knowing the candelas of the lamp,
the illuminance can be calculated by:
2
d
cd
I
=
EQUATION 5 - ILLUMINANCE FROM CANDELAS
Where: I = Illuminance in lux or footcandles.
d = Distance in feet ( footcandles ) or meters ( lux ).
Following a measurement, candelas can be calculated by:
2
* d I cd
=
EQUATION 6 - CANDELAS FROM ILLUMINANCE
H
OW TO
M
AKE AN
I
LLUMINANCE
/ I
RRADIANCE
M
EASUREMENT
Illuminance measurements are made one of two ways with the PR-655 and PR-670. The first method involves
the use of the CR-655 or CR-670 cosine receptor. The second method utilizes the use of a reflectance standard
such as the RS-3 or SRS-3.
U
SING THE
CR-655 / CR-670
FIGURE 71 - CR-655 / CR-670
1. From the Instrument Setup menu, touch the
▲▼
icons beneath Primary Accessory to scroll to CR-655 or
CR-670, depending on the instrument being used. Make any other setup changes (exposure, sensitivity
etc.) at this time. Note that only the largest aperture can be used for this accessory. The instrument will
automatically set the
Aperture selection to the largest system configured aperture.
2. Remove the current Primary Accessory from the instrument turning the accessory counter-clock-wise.