On Tue, 27 Mar 2001 10:51:57 -0600, "Doug"
>Howdy Neuman - thanks for the response. I do understand for the most part,
>but it's one thing to have an understanding and quite another to relate it
>properly. :) So let me try it this way to see if I'm still screwed up.
Or which one of us is...;-)
>Based on your response, we're in agreement that one frame of each IVS and PS
>contain the same number of scanlines. Now, my point is that while there are
>the same number of scanlines in 1/30 of a second, a PS frame's odd/even
>scanlines are all taken from the exact same point in time while an IVS
>frames odd/even scanlines are 1/60 second apart. So does it not hold true
>then, that a PS frame _does_ have twice the screen resolution for a specific
>1/30 point in time (perhaps this point is worth repeating - a specific 1/30
>second point in time), at the expense of temporal resolution?
Hmmm...
It would seem to me that if you said 1/60th second, you would be right, since IV writes one field only in
1/60th
second, and PS writes both. But, in the next 1/60 second
IV has written a new field (with new motion information),
and PS has not. If the PS-mode were ideally done, in
1/30th second they would both have the same resolution,
but the PS mode would have 1/2 the motion-change
information (its only loss would be motion-smoothness).
In practice, though, if the PS frame rate is not 30fps,
or the vertical resolution has been compromised at 30
fps (both are common occurances in PS-mode implementation...), both the time resolution and the
image definition would suffer in PS mode...
>Now you mention camcorders whose PS mode captures less scanlines, and I hear
>about certain models that can't do a full 30fps. Under those circumstances
>the choice is obvious. But as to why anyone would want a true 30fps PS
>mode...again, it's an appreciation of the look of the ouput. On my Optura,
>I've never noticed issues with subject movement...again I think this jitter
>effect is largely overstated unless the preferred method of shooting is to
>sit in an office chair and have someone spin you like a record... :)
It may depend some on the TV - a TV with "slow" phosphors
may smear motion sufficiently to give the impression
of smoothness with motion (but there should still be
no advantage for TV-viewing in using PS-mode...). With
"faster" phosphors, some jitter in legs of walking
people, passing cars, flying birds, fast pans, etc.
(that "film" effect, which I find not particularly
endearing...;-) would be visible... So, again, why
would anyone want this...? ;-)
>"Neuman - Ruether"
>news:3ad1b0df.5150653@newsstand.cit.cornell.edu...
>> Uh, what about when the *subjects* move...? ;-)
>> As for the above, methinks you don't understand
>> interlaced video vs. progressive scan... A frame
>> of IV (30 fps) has two fields split in time for
>> 1/2 frames (distributed over the screen) every
>> 1/60th second. So one *frame* of IV contains
>> 480 vertical scan lines, as does PS - but unlike
>> PS, there is more time-res. information, since
>> the 1/2 frames are each shot at 1/60th second
>> and distributed evenly in time... In addition,
>> many camcorders when they shoot PS-mode do not
>> provide as much vertical resolution in a single
>> frame as the two IV fields together, so there
>> can be a loss not only of time-related resolution,
>> but of just plain frame-resolution...
>> Again, why would anyone want this...? ;-)