[opendtv] Re: Why Europe should choose 720P for HDTV
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 13 Dec 2004 13:00:59 -0500
Doug McDonald wrote:
> It's not the "objects" (players) that are moving
> fast .... it is the fixed parts of the scene ...
> teh grid lines and the fans. This is called a
> "pan" :-) :-) The players are much less blurred
> than the background, at least the guy carrying the
> ball ... if teh pan is done right.
Doug, still photographers have used this panning
technique for a very long time, to get the speed
effect. You can often see it in magazines like
Car and Driver.
The still camera is moved *with* the moving object,
typically a fast moving car, and the shutter speed
is deliberately kept quite low, like 1/60th or
1/30th of a second. A skilled photographer will
get a rather sharp looking car, because the
relative speed between moving car and camera is low,
and a blurred background, where the relative speed
between camera and background is much higher. The
background will be streaked.
This is why I don't think the loss of vertical
resolution in interlaced images, when there's
vertical motion, is such a drastic problem.
Because resolution in any moving object (or
moving background) is lost *anyway*, due to
less than instantaneously fast shutter speeds in
the movie or TV camera. So interlaced or
progressive, a moving object or moving background
will result in lower image resolution.
What John Shutt described, with faster camera
shutter speeds available in CCD cameras now, a sort
of strobing effect, is interesting and
understandable. If the camera freezes images faster
than our eyes do, and presents these frozen images
in a sequence, I can see why that wouldn't look
natural. We would naturally expect to see blurred
images in this sequence, and are instead presented
with sharply differentiated objects in individual
frames.
This is probably a function of speed, but in small
motion, our eyes seem to have a "shutter speed" of
around 1/10th to 1/16th of a second. (From tests
done to display smooth displays in instrumentation.)
Bert
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