PR-655/670 User Manual
57
M
EASUREMENTS
M
EASUREMENT
M
ODES
Four
Measurement Modes
are available to the user:
Standard
,
L*u*v*
,
L*a*b*
and
RGB Display Cal
S
TANDARD
M
ODE
In Standard Mode the PR-655 / PR-670 performs a measurement then calculates standard photometric and
colorimetric values.
L*
U
*
V
*
/
L*
A
*
B
*
M
ODES
L*u*v* and L*a*b* measurements use photometric and colorimetric values for CIE L*u*v* or L*a*b* three
dimensional color difference calculations.
L*u*v* tests are usually made of self-
luminous samples such as LCD’s, PDP’s, EL, OLED and CRT displays.
Therefore, they are best made in a dark environment, free of ambient lighting that might influence the results.
L*a*b* tests on the other hand are typically performed of reflective or transmissive materials such as paint or
optical filters where it is necessary to provide an external light in order to measure the object. Therefore
Illuminated
samples must be selected in the L*u*v* or L*a*b* mode. Following the measurement, the light
used to illuminate the object is mathematically removed from the measurement. The resultant spectra are then
weighted by the white reference (e.g. CIE D-65) as if the sample were being illuminated by the white stimulus.
Finally, before color coordinates and eventually L*a*b* are calculated are calculated on the modified spectrum.
Color coordinates of a white reference are used during the calculation of both L*u*v* and L*a*b*. White
references stored in the PR-655 / PR-670 include D65 (daylight at 6500 Kelvins), Illuminant A (Black body
radiator at 2856 Kelvins), Illuminant B (daylight at 4875 Kelvins), Illuminant C (daylight at 6772 Kelvins),
Illuminant D50 (daylight at 5000 Kelvins), Illuminant D55 (daylight @ 5500 Kelvins) and Illuminant D75 (daylight
at 7500 Kelvins).
Following the measurement(s), L*u*v* and L*a*b* values are calculated as follows:
(
)
(
)
(
)
O
O
O
v
v
L
v
u
u
L
u
Y
Y
L
'
'
*
13
*
'
'
*
113
*
16
/
116
*
3
/
1
−
=
−
=
−
=
(
)
(
)
(
)
(
)
(
)
3
/
1
3
/
1
3
/
1
3
/
1
3
/
1
/
/
200
*
/
/
500
*
16
/
116
*
O
O
O
O
O
Z
Z
Y
Y
b
Y
Y
X
X
a
Y
Y
L
−
=
−
=
−
=
EQUATION 1 - L*U*V*
EQUATION 2 - L*A*B*
Where X, Y, Z are the measured Tristimulus values, X
O
,Y
O
and Z
O
are the Tristimulus values of the white
illuminant, u’
O
and v’
O
are the CIE 1976 u’v’ values of the white illuminant.
Содержание PHOTO RESEARCH SpectraScan PR-655
Страница 2: ...This page intentionally left blank...
Страница 25: ...PR 655 670 User Manual 9 FIGURE 10 SAMPLE EXTERNAL TRIGGER INPUT CIRCUIT DRIVERS...
Страница 106: ...PR 655 670 User Manual 90 FIGURE 87 USB POWER SCREEN Total power available Total power required...
Страница 159: ...PR 655 670 User Manual 143 PR 655 PR 670 OUTLINE DRAWINGS...
Страница 160: ...PR 655 670 User Manual 144...
