Arfa Daily wrote:
Making these still images into a perceived moving image, has nothing to do
with the persistence of the phosphor, but is a function of retinal
retention, or 'persistence of vision'. Black and white TV CRTs used a
phosphor blend known as 'P4', and tricolour CRTs typically used 'P22'. Both
of these are designated as being short persistence types. The green and blue
phosphors used in a colour CRT, have persistence times of typically less
than 100uS, and the red around 2 - 300uS.

Short and long persistance are relative terms. Compared to the P1 phosphors
of radar screens and osciloscopes, P4 phosphors are relatively short
persistence. Compared to an LED they are long persistance.

Note that there is a lot of "wiggle room" in there, supposedly the human
eye can only see at 24 frames per second, which is 50ms.

Also note that there are relatively few frame rates in source material,
NTSC TV is 30/1001 frames per second, PAL TV is 25. Film is 24, which was
stretched to 25 for PAL TV and reduced to 24/1001 for NTSC TV.

Film shot for direct TV distribution (MTV really did have some technological
impact) was shot at 30/1001 frames per second.

Digital TV could be any frame rate, but they have stuck with the old standards,
US digital TV is still the same frame rate as NTSC and EU, etc. digital TV is
still 25 FPS.

Lots of video files online are compressed at lower frame rates because of
the way they are shown. The screens still operate at their regular frame
rate, the computer decoding them just repeats them as necessary.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.