HP LP2480ZX - Manual (Page 4)

(“gamma”) may also be desirable; these are made using the optional HP DreamColor Advanced
Profiling Solution calibration tool. A data range correction may also, however, be available in the
converter used to adapt the digital video source (SDI, HD-SDI, etc.) to the HP DreamColor LP2480zx’s
digital video inputs. Please consult the user’s manual for your converter regarding the use of these
features. In any case, care should be taken to avoid having similar corrections applied by both the
converter and the monitor, which could result in an undesirable image appearance.
Emulation of studio reference monitor appearance
As noted earlier, the HP DreamColor LP2480zx is capable of very closely matching the appearance
of standard studio reference monitors, including the CRT-based products which are still common in the
industry. There are some differences between CRT and LCD display technology, though, which require
some explanation regarding the procedures for making this LCD look like the CRT you may be used
to.
The most noticeable visible differences will generally result from the different ways in which these two
technologies deal with “black level” video signals and differences in the tone response or “gamma”
curves. Properly-adjusted CRT displays are set such that the display still emits a small amount of light
when driven at the “black” level of the video signal; to set “black” so that the CRT is producing no
light (i.e., the beam is completely cut off) would result in unacceptable distortion of the lowest gray
levels. To aid in setting up CRT displays, test patterns known as “pluge patterns” (from picture line-up
generation equipment) or containing a “pluge pulse” are used. These are simply test patterns which
include a “blacker than black” region (i.e., a time during the active video when the signal is forced
below the standard black level, often to the lower “blanking” level in systems which employ blank-to-
black “setup”) generally adjacent to regions which are exactly at the “black” level, at slightly higher
gray levels, etc. A properly-adjusted CRT will show the difference between the “pluge” or “blacker
than black” area and the reference black level region, as the “black” will be slightly above the cut-off
point for the CRT, and will show the brighter grays also as distinct areas vs. the black.
On an LCD panel, “black” is generally the lowest permissible input level, and when the panel is
driven at this level, the screen will be at the lowest possible luminance. Unless the “black” signal level
is artificially increased above this point, no distinction will be seen between this and the supposedly
“blacker than black” portions of a test image. In the HP DreamColor LP2480zx, adjustment of the
Black Level control (see preceding section) can improve the appearance of such patterns in terms of
matching the appearance of a CRT, but unless additional changes are also made to the tone response
curve of the monitor, errors in the grayscale response may result. Note that, unlike on a CRT display,
the “brightness” or “luminance” control of an LCD does not affect the relationship between the video
“black level” and the display’s effective “cutoff” point (the controls generally affect only the brightness
of the LCD backlight), so adjusting the luminance control of the HP DreamColor LP2480zx will not
affect this condition.
Conclusion
The HP DreamColor LP2480zx can serve as a very accurate display in traditional video reference
monitor applications, but does have some differences vs. other products in this category (especially
with respect to traditional CRT studio monitors) that must be addressed to ensure optimum
performance in this use. Proper use of the available OSD controls, along with the HP DreamColor
Advanced Profiling Solution calibration tool and available video converter hardware where needed,
should simplify setup of the display for use in video production and related fields.