Quantum Data 881, User Manual

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640 Appendix B Image Reference
used in many different display applications. The image is self-scaling as to the number of
active pixels and active lines used. Some of the image’s elements have minor differences
from the original SMPTE specification.
These differences are noted in descriptions of the individual elements.
• The image is drawn on a reference background having a 50% intensity level. The
background covers the entire active video area.
• Crosshatch – There are 10 boxes vertically. The number of horizontal boxes is based
on the physical aspect ratio determined by the HSIZ and VSIZ parameters in the
currently loaded format. The boxes are perfectly square with any fractional spaces
placed around the outside edges of the image. The vertical lines are two (2) pixels thick
while the horizontal lines are two (2) scan lines thick. Small crosses indicate the
intersection of the horizontal and vertical lines when they are covered by other parts of
the image. All parts of the crosshatch are normally drawn using a 70% intensity level.
A 75% level is used in the secondary version.
• Resolution patch – The patch is made up of six (6) smaller boxes that are each about
6.25% of the height of the display. The boxes are made of alternating intensity (0 and
100%) stripes. The stripes run vertically and horizontally. The stripes may be one (1),
two (2) or three (3) pixels wide each. Details of the patch are shown in the lower half of
the following illustration. The patches are located in each corner of the main image and
in the center. They are oriented with the highest resolution and contrast boxes closest
to the outside corners. The 48%-53%, 48%-51% and 50%-51% level patches are
omitted in the secondary version.
• Grayscale boxes – Twelve (12) boxes at eleven (11) intensity levels are clustered
around the center of the main image. They start at 0% and increase in 10% steps to