Re: Blu-ray promises more than special menus
- From: larson@xxxxxxxxxxxxxxxxx (Alan Larson)
- Date: Wed, 19 Apr 2006 05:33:41 +0000 (UTC)
In article Gene E. Bloch <spamfree@xxxxxxxxxxxxxx> writes:
The camera takes a picture in whatever way the camera takes it. That
picture is now a fixed entity which is transmitted to the display
(perhaps through a long pipeline involving recording a tape and playing
it back later, perhaps directly over a wire, or whatever). Now the TV
displays the picture as it was captured. The picture has already been
captured; the TV has no way to change it.
Please think about this.
I have thought about this. Others have as well. The statement is true
only if you are talking about a still image.
If the image is shot in an instant, and displayed sequentially, a still
image will appear the same. A moving image will be wrong, however.
Consider a telephone pole moving across the screen. It is shot in an
instant, so the image shows it as vertical. The display shows it as
vertical. However, this is wrong, because by the time the bottom of it
is drawn on the screen, it SHOULD have moved to the side.
When your eyes track that pole moving on the screen they move smoothly
with the apparent motion, but the pole is not doing so, so it can appear
bent due to it appearing at different times to your moving eye (even though
it really isn't in the frame that was transmitted).
The only way to get it right is for the camera to match the display --
both must be "all at once" or "scanned". Artifacts can occur from mismatch
either way.
Similarly, the eyes tracking the apparently smooth motion on a screen can
result in blurring of the image when fast enough motion occurs on the screen
if the screen is continuously displayed. For example, if the image is taken
with a high speed shutter (say 1/1000 second) such that the individual frames
are reasonably sharp. Then, when the images are displayed on a perfect LCD
display (with instant update, and always on image), the eye tracking will
smear that object as the eyes track to where the object should be at that
point in time. When the image updates, it will be in the correct place again,
but the eyes will keep moving.
Had the camera taking the picture used a 1/60 second exposure, for 60 frames
per second, the object would be blurred on the recording, as the object would
have moved in front of the camera. We seem to be more used to this form of
image blur.
Alan
.
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