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Date:	Sat, 7 Aug 2004 23:01:06 PDT7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Re: OT: Video argument

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Michael Rakijas wrote:
>
> > refreshed at 60 images per second.
>
> No, 60 half images.
>
> > That's still 60 flashes per second. :)
>
> 60 flashes or a 60 refreshes but not 60 full images. If
> there are 525 horizontal lines per TV image and you get
> 262 every 1/60th of a second, what's your image rate?

60. The difference is that each field is not half of one image but a
complete image in itself. The field which immediately follows 1/60th
second later shows the position of objects 1/60th second later. If the
entire frame was snapped "at once" and then split into two fields I
would agree with you, but that "little flying dot" (for those of us
ancient ones) didn't snap everything in a petasec.

> > The digital displays on their calculators. If you wave
> > your old H-P calculator while looking at it, you'll see
> > digits frozen in the air where the LEDs blink on.
>
> And that's got what to do with TV? or anything, for that matter?

Methinks we were discussing the modulation of the display in reference
to the human eye's instant-on but slower-off tendencies. Perhaps we wuz
discussing frame rates?

> 60 flashes a second does not mean a 60 Hz image rate.

Right. But for NTSC it is 60 different images; combining each pair
gives you increased resolution plus 60 snaps per second.

> Every 60th of a second, you get every other line of the transmitted
> image. You don't get all 525 lines of the image until two flashes
> have gone by. Are you saying there's no difference? Then I presume
> you save money by going with interlaced computer displays, too.

Hmm, I'm running 60 hz but non-interlaced. I don't think my card
supports interlaced; I'll have to get out the manual and check (might be
a worthwhile test).

But there aren't 525 lines of any image. By the time the second field
arrives it shows an image that's 1/60th second later than the preceding
field.

This is why video appears so smooth, as opposed to 24 fps film. The eye
sees motion in 1/60th second increments rather than 1/24 second
increments. The resolution of film is much higher (both in "pixels"
which isn't a film term and in color saturation) but the smoothness of
motion isn't there. (Film has an aesthetic horizontal "resolution" of
perhaps 2,000 to 8,000 "pixels" depending on
stock-processing-generations and how you try to calculate it, whereas
NTSC's old "flying spot" had a horizontal resolution of perhaps 400
pixels depending on how well the equipment was aligned.)

> > This is why NTSC is so much smoother than 24fps.
>
> A 30 Hz frame rate is better 24. Even with that, text (like credits in a
> film) looks better in film than they do on TV. You're looking at it too
> simplistically. It's more than just the frame rate. I can make 60 Hz frame
> rate material look less smooth than 30 Hz by changing the optical capture
> characteristic. Frame rate is not the end of the story.

Of course not, I agree with you here. The text scrolling is a good
example of how optical capture characteristics can change the displayed
image. One fascinating part of this is the "flying spot" again -- it's
round and bigger than a line, whereas a video pixel is (usually at least
close to) square and exactly the height of a line. Thus we're putting a
round peg in a square hole (the old film scanners had "flying spots").
That poor little spot gets its sides shaved off, not to mention the
bleedover.

> One indication that videotape does not "look" better
> than film is that movies still use film for presentation

Umm, no. First, until very recently there weren't any decent theatre
video projection systems. Second, the cost of a video projection system
is much greater than a film projector. Theatres can't afford the
retrofit unless the studios underwrite the cost. Or crank popcorn up to
$75 a bucket.

> There isn't an objective characteristic
> that videotape can't equal or exceed film

I agree. I went to see "Two Brothers" so I could compare the scenes
shot with film vs. the scenes shot on video. I couldn't tell the
difference, and that's what the results of industry testing have shown
as well. But the video wasn't shot NTSC.

> People have long reacted to going to movies that were basically
> transfers of video as looking 'cheap', or like a TV show.

Yeah. They were shot NTSC and then kinescoped to film. You ended up
with all the bad characteristics of video plus all the bad
characteristics of film. What a mess.

> At 30 Hz, you can't see "strobed" motion.

You can argue that one with the NTSC developers. The reason they used
two fields per frame is because people saw the 30 hz flicker.

> > Filmmakers use video for . . .
>
> Then why do they transfer to film after they're done?

Because theatres don't have video projection systems. They have film
projectors. Last time I looked it was $100,000 per screen to retrofit
for video projection. When the prices come down you'll have more video
projection systems in the theatres.

> We should probably carry on with this off line
> so as not to go too off-topic for the group.

I have a sneaky suspicion that many on this list put me on their "kill
filter" years ago . . .

- Peter

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