writes:

It's easy. You'll need a tripod, positioned with the camera as parallel
as possible with the screen, & a shutter speed that's an *exact*
multiple of the displays refresh rate to prevent dark bars appearing in
the photo. Eg: to photograph an American TV screen (60Hz field rate,
30Hz refresh rate), you'd use a shutter speed of 1/30th, 1/15th, etc.

Mechanical shutters are just not that accurate on their own. Some
high-end video cameras have electronic shutters that can be adjusted to
almost exactly match a computer monitor, so there's only a very fine
dark or light line left moving up or down the screen, but still camera's
can't get exposures that accurate.

The simple way to get around this is to expose for 1/2 to 1 second.
That way, any spot on the screen will get about 15 or 30 refreshes of
the same image, and although there will be some portion of the screen
that gets 14 or 16 instead of 15 (29 or 31 instead of 30) the difference
becomes small enough not to see.

The more sophisticated method, used in video-input film recorders, is to
switch the video instead. They open the camera shutter with the signal
blanked, wait for vertical retrace, turn on the video and count some
integer number of video frames, then blank the video and close the
camera shutter. This obviously requires a dark enclosure for the camera
and CRT.

Dave