Quantum Data 881 - Manual (Page 331)

881/882 Video Test Generator User Guide (Rev A.22) 313
the maximum range available is (3760 - 256 = 3504) grayscale levels. Since PELD is set to
32 (24 pixel depth in the generator) the maximum number or grayscale levels that can be
rendered by the generator on a display is 1024. So if you set the
Starting Level at 25%,
the Ramp12 image will begin at the left with a grayscale level of 1132 (3504 * 0.25 = 876 +
256) and end at the right with a grayscale level of 2156 (1132 + 1024 = 2156). Because
the horizontal image resolution of the format is 1920, you would see a ramp with bands of
~2.0 pixels each (1920 / 1024 = 1.89).
RampDif image
This image has two ramps. One on the top and one on the bottom. It enables you to show
a contrast of color depths. For example you can specify that the top ramp use
12-bit/component deep color and the bottom ramp 10-bit color. You can then view the
image and see whether banding occurs and how pronounced, in the either of the ramps. If
the display under test supports 12-bit/component color, the top ramp will show a near
uniform ramp on the top (depending on the horizontal resolution of the active format). The
bottom ramp will show more pronounced banding because the range of the ramp is
greater than the color depth.
This image is used to view two specific range of grayscale or color levels (ranges up to
512) throughout the entire range allowed by deep color support in the generator (i.e. 36 bit
or 4096). You need to set the pixel depth in the generator to 24 bit (PELD = 32) in order to
access 512 grayscale or color levels on a single image rendered on a display. The
following is a sample of the RampDif image is rendered on a display.