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10 | NEC Display Wall Calibrator - UsEr's GUiDE
2
Introduction to display monitor calibration
The screen image on color LCD displays is created by emitting white light from a backlight source such as cold
cathode fluorescent lamps (CCFLs) and then passing it through individual sub-pixels with red, green and blue filters
which form each pixel on the screen. The amount of light that is allowed to pass through each pixel is controlled to
form an image on the screen. The color of each pixel is controlled by varying the ratios of light passing through each
of the red, green and blue sub-pixels.
The overall brightness or Intensity of the screen is controlled by adjusting the brightness of the fluorescent lamp
backlight, however the adjustment range of the backlight is limited. If it is necessary to adjust the Intensity below the
level achieved by adjusting the fluorescent lamp backlight alone, further adjustments can be made using the internal
LUTs (look up tables) in the display which control the light that passes through each individual pixel.
Likewise, White Point adjustments to the display are made using the internal LUTs to reduce the brightness of one
or more colors (red, green, or blue).
Before calibrating, the desired color characteristics of the calibrated video wall must be selected. In NEC Display
Wall Calibrator these characteristics are called Calibration Targets. The software adjusts the monitors to the color
characteristics in the selected Target.
When calibrating a video wall, careful consideration should be made as to how the displays will be calibrated so that
they match as necessary. The video content shown on the displays, and how it will be divided on individual displays
will determine some of the calibration settings.
For example, when using a video wall consisting of several displays that will be displaying video tiled across all of the
displays simultaneously, it is essential that all of the displays match in both White Point and Intensity (brightness).
However, if for example, the displays each show separate video on their screen, then the Intensity matching between
the displays may not be as important as having each display be as bright as possible. Having the displays match in
White Point only may be sufficient.
The NEC Display Wall Calibrator system provides the flexibility for meeting different scenarios such as these.
When calibrating a video wall to match in both White Point (color) and Intensity (brightness), the Target Intensity
can only be as high as the dimmest display. This is why it is necessary to first measure all of the displays in their
native or uncorrected state to find out the native White Point and Intensity values for each display. From these
measurements, the lowest common Intensity value for the chosen White Point can be calculated by the software.
About Calibration Targets
A Calibration Target consists of up to four specifications that describe the color characteristics of the display:
Intensity
•
White Point
•
Gamma or Tone Response Curve (TRC)
•
Contrast Ratio
•
Calibration overview
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