B&K Precision 1253 - Manual - Manual (Page 24)

Display Calibration
Important Notes: The information in this document describes how the BK Precision BK-1253 HDTV Test Pattern
Generator may be used to calibrate and verify the performance of HDTV display products. This information is
applicable only to the BK Precision BK-1253 .
1. Black-level (Brightness) Calibration
Correct black-level calibration is critical to achieving a picture with full contrast and subtle details in dark shadow
regions. Black-level is calibrated by adjusting a display’s Brightness control using a PLUGE (Picture Line-Up
Generator Equipment) pattern. The BK-1253 provides a variety of PLUGE patterns to make the most accurate
black-level adjustment possible.
Professional HDTV standards specify that black corresponds to a video signal level of 0 volts (0-IRE). The display’s
black-level circuits must be adjusted to produce minimum light output for a 0-IRE input signal. If the Brightness
control is set too high, the display will not be able to produce black at all. The darkest areas of the picture will only
be dark-gray and the picture will appear washed-out, lacking in vivid contrast.
If the display’s Brightness control is set too low, portions of the picture that should be dark-gray will be produced as
black, and everything darker in the picture will also appear as black. In other words, several levels of dark gray in
the picture will be crushed into black and the picture will look overly harsh, lacking in dark shadow details.
One measure of display quality is how well the black-level remains fixed as the average picture (brightness) level
(APL) of the incoming video changes. Only the finest displays maintain a constant black-level with large changes in
APL. In the majority of CRT-based displays the black-level adjustment must be a compromise over a range of
APLs. The BK-1253 provides a Window pattern with PLUGE bars, so the APL may be altered to make the best
setting.
Properly calibrated CRT-based displays should be able to produce fully black picture areas; i.e. a complete
absence of light output. But fixed-pixel display technologies like LCD (Liquid Crystal Display) and DLP (Digital Light
Processing) projectors have not been able to produce total black. It is even more important that the black-level in
those display devices be accurately adjusted to minimize light output for black video signals.
BK-1253 Black-level Adjustment Patterns:
PLUGE Window
SMPTE Bars
Flashes between 0 and -5 0 +5 0 -5 0 0 -5 0 +5
Adjustable
0 to 100
-5: Blacker-than-black, -5 IRE (2.5 IRE for NTSC)
0: Black, 0 IRE (7.5 IRE for NTSC)
+5: Lighter-than-black, +5 IRE (12.5 IRE for NTSC)