B&K Precision 1253 - Manual - Manual (Page 26)

than is a full screen measurement. Most fixed-pixel projection systems produce the same brightness in full fields as
small areas because they have fixed brightness sources provided by projection bulbs.
BK-1253 Contrast Adjustment Patterns:
The BK-1253 has several patterns that can be used together to determine the best operating point for the Contrast
control. These include the Window, Multiburst, PLUGE, Needle, Overscan-Bounce , and Grey Raster patterns.
Contrast Calibration Procedure:
The Contrast control can be initially set to the desired target level by using a Color Analyzer to measure the
brightness of the white rectangle in the Window pattern set to 100 IRE Grayscale (maximum). The black-level can
be re-checked using the PLUGE stripes on the left side of that pattern. After ensuring that the black-level and 100
IRE white levels are simultaneously correct check for any of the undesirable side effects discussed below.
Use the Multiburst pattern to check for a loss of resolution at the desired Contrast level. If the upper bands of the
Multiburst pattern become significantly more distinct at a lower Contrast level, then a lower brightness level may be
warranted.
100 IRE
If the Contrast control is turned up too high a CRT spot may bloom, or expand excessively. Use the inner horizontal
staircase of PLUGE pattern to check for spot blooming. If the 100 IRE rectangle is wider than the rectangles below
it, then spot blooming is the likely cause. Reduce the Contrast control until the rectangles are the same width. Spot
blooming can damage CRTs.