Calibrating Fixed-Pixel Displays
				A CRT type display can produce a small spot of light at any position along a horizontal scan line. Any other type of display, though, has an absolute fixed number of pixel positions along each horizontal scan line. These fixed-pixel displays (plasma, DLP, LCD, LCoS, etc.) can produce a small spot of light only at each fixed-pixel position and not at any position in between.
Besides having fixed pixel positions, these types of displays are calibrated slightly differently, due to their different operating characteristics. The main differences are the displays’ different light output characteristics, compared to a CRT type display, and the effects of misadjustment of the contrast control. You can calibrate fixed-pixel displays with the CP5000 All-Display Color Analyzer, which accurately measures the light output of any type display, and the S802B Multimedia Video Generator, which provides test patterns specially suited to fixed-pixel displays, and has a DVI output option. To calibrate a display, you should first preset the brightness and contrast controls for an approximately correct adjustment. Then, you should calibrate the white balance/gray scale tracking. Finally, you should calibrate the user-menu defaults for the major user controls.
Preset the Brightness and Contrast Controls Brightness Control The brightness control adjusts the light level of the darkest portions of a picture - that’s why this control is more accurately called the black level control.  When the black level is set too dark, the subtle dark gray details of a scene are lost to black.  When the black level is set too bright, the darkest grays and deep blacks in the picture are all a lighter gray, which lowers the contrast ratio of the display, reducing picture quality. The S802B Pluge pattern, shown in Figure 1, provides a unique black level alignment signal, designed for easily adjusting the brightness control for proper black level.
Fig 1: The Pluge pattern is used to adjust the television brightness control for proper black level.
Note: The environment surrounding a TV affects the proper setting of the user controls. Room lighting should be adjusted to the preferred level for movie viewing before the TV is calibrated. When the Pluge pattern is selected with the NTSC format, the S802B automatically displays an NTSC Pluge pattern with a 7.5 IRE black setup level. When an HDTV format is selected, the S802B displays an HDTV Pluge pattern, without black setup. To adjust the brightness control on an NTSC or HDTV display device with the Pluge pattern, watch the second box from the inside, which is alternating between black and blacker-than-black (7.5 IRE and 3.5 IRE in NTSC, 0 IRE and –4 IRE in non-NTSC formats).  Adjust the brightness control until the black and blacker-than-black levels appear the same and no brightness alternation can be seen.  The outer 10 IRE box should still be slightly visible.  The same method is used for HDTV, although the pattern IRE levels are different. Contrast Control The contrast control is sometimes labeled the picture control, or is more accurately called the white level control. This control adjusts the light level of the white or high luminance portions of a scene. If the contrast control is set too low, the image is dim, the whites become dull and the image loses its luster. The optimum adjustment of the contrast control is as high as possible without creating any ill picture effects. This is different in CRT type and fixed-pixel displays.
Since a fixed-pixel display (anything but CRT) has an absolute threshold of maximum light output, when the contrast control is set too high on this type of display, brighter white objects all become the same brightness level. On a staircase test pattern, this can be seen as the brighter steps starting to blend together at the same brightness level. A staircase pattern isn’t as useful as it could be for setting the contrast control, however, as the bars take very large brightness steps. Fig 2: The Hi-Lo Track pattern is used to adjust the contrast control for maximum white level without compression on fixed-pixel displays.
The S802B Hi-Lo Track pattern includes 100%, 97.5%, and 95% luminance areas, which allow you to easily detect small amounts of white compression. On a fixed-pixel display, adjust the contrast control high enough to cause the bright white rectangle to just start blending into the full white background. Back the control off just slightly to be sure there is no white compression occurring, and the contrast control is optimally adjusted (you should be able to see three bright white levels on the lower half of the pattern). You should recheck the brightness control after you adjust the contrast control, as the two controls may have some interaction. White Balance Adjustment Once the brightness and contrast controls are preset, you are ready to calibrate the display’s white balance. Following is a general white balance/gray scale tracking adjustment procedure that works well for most displays. If a service manual is available for the display, however, use the manufacturer’s adjustment procedure.
1. In the CP5000 setup utility, select the white reference or CIE chromaticity coordinates to which you wish to adjust the display. Note: Displays should be adjusted to the CIE D65 daylight standard (x = 0.313, y = 0.329) for best color accuracy with color program material. For B/W movies, 5500 K (x = 0.332, y = 0.341) does an excellent job of emulating cinema theater presentations. 2. Select the S802B Window1 pattern, press the Step button, and rotate the Image knob to adjust the window for 70-80 IRE (toggle the Step button to select other test patterns). Fig 3: Select your desired White Reference for white balance in the CP5000 setup utility.
3. Adjust the drive/gain controls to obtain color balance at high luminance, as indicated on the CP5000 Delta RGB display. Note: If only two drive controls are available, select the missing color as the adjustment reference color in the CP5000 Delta RGB display window. Fig 4: Select one color as the adjustment reference color on the CP5000 Delta RGB display, then adjust the other two color controls on the display to balance the CP5000 Delta RGB graphs all to zero.
4. Select the S802B Window2 pattern and adjust the window for 15-20 IRE. 5. With green selected as the adjustment reference color in the CP5000 Delta RGB display window, adjust the red and blue cutoff/bias to obtain color balance at low luminance. Fig. 5: S802B  100 IRE Window pattern
6. Re-select the Window1 pattern, at 70-80 IRE, and recheck/readjust the drive controls for color balance at the selected white reference. 7. Repeat steps 3-6 until the display’s white balance remains relatively constant (tracks) over the full range of white window IRE levels. A DExy of 10 or less over the entire gray scale is a good goal.
Final User Control Adjustment When you have completed the white balance adjustment, perform a final calibration of the display’s user controls (brightness, contrast, sharpness, color, and hue). Preset the user-menu controls to their factory-default condition. Then access the “sub” controls in the service menu (subbrt, subcnt, subcol, etc.). Calibrate the user “sub” controls for proper operation under the darkest conditions in which the customer will watch movies. For daylight operation, the customer can adjust the brightness control higher for proper black level under the higher ambient light condition. Then, for fully calibrated nighttime movie viewing, he can simply select the factory reset to return to your fully calibrated movie mode. Calibrate the brightness and contrast controls, as you did previously, then finish by calibrating the sharpness, color, and hue controls. Sharpness Control The sharpness control was originally designed to put back some of the high frequency picture detail that was lost with older luma/chroma notch filters. Modern TVs now all use a comb filter, which doesn’t lose high frequency luminance detail. Even if there is no longer a need for the sharpness control, manufacturers find it difficult to take away a feature that consumers have seen on sets for years. If the sharpness control is improperly adjusted, however, it either adds picture distortion or reduces picture resolution. The S802B Sharpness pattern works very well for adjusting the sharpness control. The Sharpness pattern contains white lines running through a black background and black lines running through a white background. These lines are commonly referred to as needle pulses.
While adjusting the sharpness control, watch the left and right edges of the needle pulse lines. If the sharpness is set too high, a faint duplicate line will be seen beside the original line. This ghosting affect is unwanted picture distortion. If the sharpness control is set too low, the needle pulses will appear out of focus and the image will lose its resolution. Adjust the sharpness control to achieve the best balance between ghosting and poor focus or resolution. Fig. 6: The Sharpness pattern is used to properly adjust the television sharpness control.
The top, multiburst section of the Sharpness pattern can also be used as a reference to adjust the sharpness control. Starting with the sharpness control at its minimum setting, increase the control until all five bursts are at equal brightness levels, but not high enough to cause ghosting lines adjacent to the widest multiburst stripes at the left.
Color and Hue Controls The color and hue user controls should be adjusted last. These two controls should be adjusted using the S802B SMPTE color bar pattern. The easiest and most accurate method of adjusting the hue and color controls is to view the SMPTE color bar pattern through a blue filter. Color Control Adjust the color control by comparing the intensity of the large top outside blue and white bars with the intensity of the small bars below them. These bars are indicated in Figure x. Adjust the color control to make these bars appear the same light level, as viewed through a blue filter.
Fig 7: The SMPTE bar pattern blue and white bars are used to calibrate the television color control.
Hue Control Adjust the hue control by comparing the intensity of the cyan and magenta color bars through a blue filter. These bars are indicated in Figure x. Compare the light level of the large top cyan and magenta bars with the small bars directly below each of them. Adjust the hue control to make these bars appear the same light level, as viewed through a blue filter. To double-check the adjustment, remove the blue filter and observe the yellow and cyan bars. If the hue is set too red, the cyan bar will look green and the yellow bar will look orangeish. If the hue is set too green, the cyan bar will look blue and the yellow bar will look greenish.
Fig 8: The SMPTE bar pattern cyan and magenta bars are used to calibrate the television hue control.
High Quality Video Calibrations The CP5000 ColorPro Color Analyzer, with its capability of accurately measuring light from any type display, and the S802B Multimedia Video Generator, with its fixed-pixel display test patterns, are a perfect combination for calibrating fixed-pixel displays. You can use this versatile pair of test instruments to perfectly calibrate any video display for optimum presentation of high quality images. Satisfy your customers by calibrating their displays for the highest quality pictures they’ve seen yet.