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Appendix B
StillColor
©
National Instruments Corporation
B-3
PCI/PXI-1408 and NI-IMAQ for Win95/NT
it impossible to separate the two signals perfectly and, therefore, perfect
reconstruction of the original color image is not possible.
All of the traditional ways to separate the two signals result in visual
artifacts on the final picture. Techniques such as frequency-band
filtering or comb filtering can minimize some of these artifacts, but
most techniques are optimized to obtain the best picture for
visualization of a continuous acquisition. The composite color formats
are designed so that artifacts resulting from one frame are almost
cancelled by artifacts in following frames. This system takes advantage
of the slow response time of the human eye to obscure most of these
problems.
The situation is different in a single frame acquisition where a single
image is needed. A single image usually clearly shows the result of a
bad color/luminance separation. Typical weakness of traditional
separation techniques are:
•
Reduced luminance bandwidth, resulting in a blurry image.
•
Cross-color modulation where rapidly changing colors affect the
luminance of the image, as shown on the edges of the parrot’s head
in Figure B-1.
•
Cross-luminance modulation where rapidly changing luminance
(stripes) results in irritating random color patterns, as shown on the
black and white stripes around the parrot’s eye in Figure B-1.