Quato iColor Display 3.7, Руководство пользователя

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8
Color Difference
The human eye has a quite different sensitivity for
color difference between colors and grays. Plus, the
eye is a different sensitivity in different color regions.
In general, one can say, that color deviations can be
recognized from 3
∆
E on. With some colors, it will be
below
∆
E 3, with some colors above this treshold.
Deviations in a gray balance or between grays are
already observed from 1
∆
E on. Deviations above 3-5
∆
E (colors) and 1
∆
E (grays) are visible for the trained
eye.
Measurement Devices for Displays
There are two types of colour measuring instrument.
Colorimeters, as the name implies, see colors. A
colorimeter has sensors that, in much the same way
as the human eye, break the wavelengths of light
down into red, green and blue areas. Colorimeters
are most often used to measure the colour emitted
by displays. The second way to measure color is with
a spectrophotometer. A spectrophotometer can mea-
sure the wavelengths of light emitted from a light
source or reflected by an object. They are the best
way to measure colour. However, on displays, spec-
trophotometers suffer from poor precision in dark
areas. Here colorimeters are much better suited. On
the other hand, a colorimeter need to be trained on
a certain display type to be accurate. Therefore, a
device correction is needed for displays that differ
from the standard (like Wide Gamut or White-LED/
RGB-LED). A spectrophotometer does not need any
kind of training.
Display Basics
A display uses an additive color system where the
addition of red, green and blue results in white. So
far the theory. Unfortunately, the real world is diffe-
rent. With printers and the used subtractive system,
cyan, magenta and yellow should result in black.
However, the result is not a pure black, but some-
thing olive. That´s why we use blank ink in addition.
For displays, red, green and blue may result in some
kind of white, but at different luminance levels, their
behaviour is quite non-linear. Plus, a display is not a
pure additive system; it´s a bit more like a transmis-
sive system. The light from the back (either CCFL or
LED) passes the color filters and the TFT itself. In the-
ories, the secondary additive colors cyan, magenta
INFO
The deviation between two colors is expressed in Delta Error,
short DeltaE or
∆
E. In most cases, a pure
∆
E is based on the
1976 color difference formula based on the L*a*b* system.
The Quato software uses this standard DeltaE Lab or DeltaE
1976 formula. If other formulas (like
∆
E 94 or
∆
E 00) are used,
the Quato software expressively informs about this.
Additive colors (left) and subtractive colors (right). The primary
colors always mix to the secondary. And the secondaries of one
system are the primaries of the other one (and vice versa).