HP DreamColor LP2480zx Professional manual Bits/color LCD Module, LED Backlight Unit

Table A-2Supported Signal Inputs and Color Space Matrix (continued)

Input used	Color encoding	Scan format	Result
Component, CVBS, S-Video	YUV (RGB not supported)	Either	Color Space presets: disabled
			Hue/Saturation controls:
			enabled

10 bits/color LCD Module

As noted earlier, the LCD module in the LP2480zx monitor provides a 10 bits/color (30 bits/pixel) input, with true 10-bit drivers within the LCD itself. This means that each primary (red, green, and blue) may be controlled over 1,024 steps (input codes 0 to 1023) from the black level to the white (peak luminance for that color). This results in over 1.07 billion separate colors available within the display’s gamut, versus approximately 16.7 million for a conventional 8 bits/color display.

This increase in dynamic range is required for the accurate display of color within the wide gamut provided by the LP2480zx’s LCD, and especially for achieving the necessary degree of color accuracy within the more restricted gamuts that this monitor is capable of providing when emulating various standard output devices. Increasing a display’s color gamut – the area covered by the display when the primaries are plotted on a standard chromaticity diagram – would result in a greater difference between adjacent colors if the degree of control (bits per color) for each primary were not also increased. Increasing the bit depth of the display drivers achieves this without the possibility of undesirable image artifacts which may result from temporal or spatial dithering as may sometimes be used with an LCD of lower inherent accuracy. (The LP2480zx’s “front-end” electronics are also, however, capable of providing temporal dithering, if needed, to increase the delivered accuracy beyond the 10 bits/color level. By default, this is used only between the pre-LUT and the 3x3 matrix multiplier stage; temporal dithering is possible but normally disabled at the 30-bit connection between the post-LUT and the LCD module itself.)

With most video sources (which typically provide video information at the standard 8 bits/color or 24 bits/pixel), and across all of the LP2480zx’s various inputs, the increased accuracy of the LP2480zx LCD module is used to provide more accurate color within the selected standard color space. However, 30-bit sources may also be directly supported using the DisplayPort 1.1 and HDMI 1.3 inputs only. This will be of greatest benefit when the LP2480zx is used in the wider-gamut modes (such as Full, Adobe RGB, DCI).

LED Backlight Unit

As noted earlier, the LP2480zx monitor employs a backlight consisting of an array of red, green, and blue light-emitting diodes (LEDs) rather than the more typical cold-cathode fluorescent lamps (CCFLs) on most LCD monitors. This provides several significant advantages, in addition to the obvious benefit of a wider color gamut (that is, more saturated primaries) than can currently be achieved using CCFLs. In the LP2480zx, the red, green, and blue LED arrays are controlled both collectively and separately by a dedicated backlight controller, which permit both very accurate setting of the display luminance as well as control of the white point of the unit. Color sensors in the backlight unit feed color information back to the controller constantly, permitting an accurate white point to be maintained.

Compared with CCFLs, which have only a limited range of brightness control available and a fixed emission spectrum, the LED backlight used here provides a very wide range of both brightness and color control. The white point may be adjusted over a range corresponding to a correlated color temperature (CCT) of 4,000K to 12,000K, including support for all standard white points with CCTs within this range. In addition, the white luminance may be adjusted from a maximum of approximately 250 cd/ m2 down to 50 cd/m2, making the LP2480zx suitable for use in low-light environments; at the lower

38 Appendix A Advanced Color Management Features and Usage