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Digital Video and HD
book

Digital Video and HD

by Charles Poynton
January 2003
Intermediate to advanced content levelIntermediate to advanced
736 pages
30h 54m
English
Morgan Kaufmann
Content preview from Digital Video and HD
Visual acuity
When an optometrist measures your visual acuity, he or
she may use the Snellen chart, represented in Figure 1.8
in the margin. The results of this test depend upon
viewing distance. The test is standardized for a viewing
distance of 20 feet. At that distance, the strokes of the
letters in the 20/20 row subtend one sixtieth of
a degree 1 o
(/6o, one minute of arc). This is roughly the
limit of angular discrimination of normal vision.
Visual angles can be estimated using the astronomers'
rule of thumb depicted in Figure 1.9 in the margin:
When held at arm's
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Publisher Resources

ISBN: 9781558607927