Jadak Photo Research SpectraScan PR-7 Series, Руководство пользователя

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Chapter 5
– Setup Menu
48
M
EASUREMENT
M
ODES
Five Measurement Modes are available to the user: Standard , L*u*v* , L*a*b* and RGB Display Cal and
optional Color Rendering Index (CRI) .
S
TANDARD
M
ODE
In Standard Mode the PR-7XX performs a measurement then calculates standard photometric and colorimetric
values. Calculated values include Photometric (luminance, illuminance, luminous flux and luminous intensity
depending on the accessory in use), CIE 1931 xy, CIE 1960 uv, CIE 197
6 u’v’, Correlated Color Temperature
(CCT), micro-reciprocal Kelvins (mk-
1) and deviation of sample from Planck’s locus in CIE 1960 uv values.
L*
U
*
V
* / L*
A
*
B
* M
ODES
L*u*v* and L*a*b* measurements use photometric and colorimetric values to perform 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*u*v* measurements are typically made in the
Self-Luminous calculation mode.
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* values 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-7XX 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’ and v’ are the CIE 1976 values, and u’
O
and v’
O
are the CIE 1976 values of the white illuminant.