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<strong>Veritas</strong> <strong>et</strong> <strong>Visus</strong> <strong>Display</strong> <strong>Standard</strong> February 2009<br />
Photom<strong>et</strong>ry and colorim<strong>et</strong>ry measurements: This section presents photom<strong>et</strong>ry and colorim<strong>et</strong>ry measurements for<br />
the LCD models from LG, Samsung, Sharp and Sony. Three of the units are the current top-of-the-line flagship<br />
models. All of the units were s<strong>et</strong> up for optimum image and picture quality using only standard user menus and user<br />
controls. The selections and s<strong>et</strong>tings were all chosen to have each unit perform as closely as possible to a high<br />
quality HDTV studio monitor. In particular, all s<strong>et</strong>tings that dynamically process the image were disabled, such as<br />
dynamic contrast, dynamic backlight, dynamic black, dynamic white, and dynamic color. Many of these functions<br />
are given propri<strong>et</strong>ary names by each manufacturer.<br />
The units were all fed digital HDMI signals. <strong>Display</strong>Mate test patterns were used to accurately s<strong>et</strong> the black level to<br />
16, the peak white clipping level to 255, and the white point chromaticity as close to D65 as possible. The<br />
measurements were made after a minimum one-hour warm up period with a Konica Minolta CS-200<br />
Spectroradiom<strong>et</strong>er s<strong>et</strong> for a 1-degree acceptance angle.<br />
Luminance and contrast ratio: Table 3 summarizes the principal photom<strong>et</strong>ry measurements. The “Highest<br />
Calibrated Luminance” is the maximum luminance that the unit can produce while calibrated as described above.<br />
For most LCDs, this was obtained from the highest backlight s<strong>et</strong>ting available. For side-by-side comparisons the<br />
backlight for each of the LCD units was adjusted to provide comparable luminance, about 200 cd/m 2 for the largescreen<br />
flagship units, and somewhat higher at about 250 cd/m 2 for the mid-line units.<br />
Highest<br />
Calibrated<br />
Luminance<br />
Peak<br />
Luminance<br />
S<strong>et</strong>ting Used<br />
69<br />
Contrast<br />
Ratio<br />
Correlated<br />
Color<br />
Temperature<br />
Gamma<br />
Samsung LCD 427 cd/m 2 189 cd/m 2 1,877 7035 K 2.25<br />
Sharp LCD 307 cd/m 2 192 cd/m 2 1,330 7334 K 2.23 - varies<br />
Sony LCD 362 cd/m 2 202 cd/m 2 1,344 6495 K 2.17<br />
LG LCD 384 cd/m 2 251 cd/m 2 511 6463 K 2.13 - varies<br />
Table 3: Photom<strong>et</strong>ry and colorim<strong>et</strong>ry measurements summary<br />
Source: <strong>Display</strong>Mate Technologies and Insight Media<br />
Transfer function and gamma: Figures 3 to 7 plot the transfer functions for various combinations of the HDTVs.<br />
The plots extend down to 10% of peak signal intensity, which corresponds to 0.0063 of the peak luminance for the<br />
standard gamma of 2.20.<br />
Gamma is a param<strong>et</strong>er that specifies how the luminance changes with signal input level. Originally based on the<br />
performance of the CRT, the luminance “L” is presumed to vary with signal “S” as a pure mathematical power-law<br />
in the form L2/L1 = (S2/S1) Gamma . In particular, when plotted on a log-log graph the slope of any portion of the<br />
transfer function is its local gamma. If the transfer function is a perfectly straight line on a log-log graph, then<br />
gamma is a constant. If it isn’t a straight line then gamma varies with signal level.<br />
The logarithmic slope of the transfer function is the gamma for the display, which is listed for each unit in Table 3.<br />
When the transfer function is not a perfectly straight line on a log-log graph, then the gamma varies over the signal<br />
intensity range. The gamma values listed in Table 3 were measured over the signal intensity range from 90 to 40%<br />
of maximum. The ideal standard gamma value for HDTVs is 2.20.<br />
Note that if the transfer function is not a perfectly straight line, then the effective gamma changes with anything<br />
that affects the operating points for the signal intensity range, such as the s<strong>et</strong>ting of the contrast/picture control or<br />
any other function that affects video gain or signal levels.