Converting TTL monitor to Analog ( Screen Flicker)(Human visu al response OT)

From: McFadden, Mike <mmcfadden_at_cmh.edu>
Date: Fri May 11 11:24:30 2001

Actually the human visual response in variable depending on what part of the
field of vision is used. I can and many people can see flicker using your
peripheral vision. Pointing your head away from the screen about 60 degrees
and looking at the screen from the corner of you eye you can commonly see
flicker. Rods and cones in you eye respond differently to color, flicker,
and light levels.

There are whole books on human visual response and lots of study of the
field when looking at Radiological images. The new "hot topic" is Radiology
is "soft-copy" reading of medical images, skip the film use a computer
monitor. The problem is that clinical quality monitors cost
$10,000-$20,000. Everybody want consumer grade monitors with the associated
low cost. Brightness variability across the screen is routinely 25%.
Examining images for lung cancer nodules or mammography lesions are
examples. There is a huge equation that lists visual response which is tied
to brightness, apparent contrast, wavelength, and size. Lots of human
response is below the "threshold of awareness". If you can obviously see
the lung nodule then your chances of treatment and 5 year longevity are
reduced.

Mike
mmcfadden_at_cmh.edu
Received on Fri May 11 2001 - 11:24:30 BST