piclist 1997\09\16\181931a >
Thread: POV - was Multiplexing Seven Segment Displays [OT]
picon face BY : John Payson email (remove spam text)

> >> I have heard of people that get headaches watching commercial movies
> >> because the 1/24th of a second frame rate flickers dramatically to
> >> them.
>     I don't really notice it much in movies, except when there is panning
> going on, then it is REALLY bad.

Modern movie projectors flash the screen twice for each frame (resulting in
a 48hz flash rate); 8mm projectors flashed 3x/frame (resulting in a 54Hz
flash).  For stationary pictures, the double-flash helps reduce flicker.  It
has the annoying side-effect, however, that moving images appear "doubled"
and blurry.  If you focus on any light object as it travels across the screen
(and track it with your eye) you'll notice that you see "two" of them while
they are moving.  The same thing also happens on scrolling displays which are
scanned more than once per scroll (the worst is displays that scroll a line at
a time at about 20-30fps); anyone driving scrolling displays with a PIC (or
any other CPU) should keep that in mind.

In reply to: <PICLIST%97091617335994@MITVMA.MIT.EDU> from "Herbert Graf" at Sep 16, 97 05:22:34 pm
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Subject (change) POV - was Multiplexing Seven Segment Displays [OT]

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