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Date:	Sat, 7 Aug 2004 21:40:02 PDT7
From:	"George M. Boyd" <bb385@lafn.org >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Re: OT: Video argument

Content Type: text/plain

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Michael Rakijas wrote:
> =====================================================
> If you are responding to someone asking for help who
> may not be a member of this list, be sure to use the
> REPLY TO ALL feature of your email program.
> =====================================================
>
> ** Reply to message from Peter Skye on Sun, 11 Jul 2004
> 18:03:16 PDT7
>
>
>>Michael Rakijas wrote:
>>
>>Oh boy! Somebody to argue with!
>
>
> Oh, brother ... fine, have it your way.
>
>>>Most people find TV refresh rates acceptable
>>>despite the 30 Hz image rate.
>>
>>This is incorrect. TV images (NTSC, standard North American television)
>>are 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?
>
>
>>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?
>
>
>>>>Many people don't realize that television (NTSC) is shot at 60 images
>>>>per second.
>>>
>>>Again, see above - this is the half image rate.
>>
>>Rocky, there are still 60 flashes per second. Each flash contains an
>>updated view of the image, i.e. the image 1/60th of a second later.
>
>
> 60 flashes a second does not mean a 60 Hz image rate. 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.
>
>
>>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.
>
>
>>>There are two things going on here that shouldn't be confused:
>>
>>And why not? I _am_ a life-long registered Republican.
>
>
> No comment.
>
>
>>>Videotape looks cleaner mostly because of its improved characteristics
>>>in color fidelity and linearity relative to film
>>
>>No. Videotape looks much better than film even when viewed on a black
>>and white television. And film has far superior shadow characteristics.
>
>
> I guess we'll just have to disagree on this one. One indication that videotape
> does not "look" better than film is that movies still use film for presentation
> - movies would have transitioned a long time ago. I'm not saying that video
> isn't better. There isn't an objective characteristic that videotape can't
> equal or exceed film (except possibly dynamic range which is what would be
> reflected in the shadow characteristics mentioned above). Yet film "looks"
> better because it's what we're accustomed to. People have long reacted to going
> to movies that were basically transfers of video as looking 'cheap', or like a
> TV show. They go to a movie and they don't expect it to be 'cheap' in quality
> despite the fact that video is objectively higher in quality. So, we continue
> to see film and probably will continue to see "film" (in digitized transfers)
> even when we get to all digital transmission systems.
>
>
>>>but most don't find it acceptable for movies because
>>>the film going public has been conditioned to expect film and its
>>>characteristics, that is, the softness and relative warmness (opposite of
>>>harshness) relative to videotape.
>>
>>I went to see Two Brothers on Friday (the film about the tiger cubs).
>>Part of it was shot in HDTV for production reasons and then transferred
>>to film. I looked hard but couldn't see the difference.
>
>
> That explains a lot more. In fact, a great deal of effort has gone into making
> computer generated and videotaped productions as pleasing to the eye as film.
> The simple method is just to transfer to film. My guess is that this will
> transition to digitally processed productions in which the film "look" is
> imposed on the image sequence of digitally captured or generated video.
>
>
>>>Flickeryness and smoothness of motion are related to . . .
>>>video capture rate and image capture (shutter) speed.
>>
>>Capture rate yes. Shutter speed yes with the caveat that blurred motion
>>is smoother than "strobed" motion.
>
>
> I guess we'll just disagree some more. At 30 Hz, you can't see "strobed"
> motion. However, at a fixed refresh rate (say 30 Hz), you can see the
> difference between film/video/image where the shutter speed varies between the
> minimum, which is the inverse of the image rate (or 1/30th sec in this example)
> and say 1/1000th of a second where the shutter is very fast and is capturing a
> less blurred still image each frame. I think you would call this "strobed"
> motion but each image is, in fact, cleaner just as it would be in photographs
> and yield a better movie. In this case, "better" means cleaner (objectively
> measured) to see rather than more pleasing in the film versus video debate
> above.
>
>
>>>This has led to the process of filmmakers using video first (for the added convenience as
>>>well) and then transferring to film to cater to the film going public.
>>
>>Not a chance. Filmmakers use video for 1) its lower cost, 2) there are
>>production problems which video resolves (like putting cameras in tight
>>places or where low weight is required or where you need to set up a lot
>>of cameras), 3) they simply want that particular "look" (talk to the
>>lighting director and find out how hot and shadow you'll deal with).
>
>
> Then why do they transfer to film after they're done?
>
>
>>>>Note that the eye can "see" extremely short "changes". A photographic
>>>>strobe light might be "on" for just 1/1000th of a second and yet we
>>>>still see it.
>>>
>>>Even neurons have a persistence to them. I don't think the question here is
>>>how short of an image change one can see (the eye has an integrating effect) but
>>>how far apart two strobe pulses need to be before you perceive them as two
>>>separate pulses. I guarantee that two 1/1000th of a second pulses separated by
>>>1/1000th of a second will be perceived as one pulse. It's been a long time
>>>since I've looked at this stuff but I think that they have to be separated by at
>>>least low 10s of milliseconds to be perceived separately.
>>
>>Try flashing those pulses on two different sides of an object. Or
>>flashing them in different colors. I don't know what the results will
>>be but I know the eye is non-linear with respect to the three cones,
>>i.e. they resolve differently.
>
>
> Timing is extremely important. If you flash on two different objects close
> enough together, you get a mixing effect.
>
>
>>Glad to know somebody read my message. Whatcha up to, Rocky?
>
>
> Eh, just real busy as evidenced by the time it took for me to respond to your
> challenge. We should probably carry on with this off line so as not to go to
> off-topic for the group. I won't be able to go to the next meeting (visiting
> relatives in Philly) but maybe the next meeting.
>
>
>>- Peter
>
>
> -Rocky
>
Hey, keep it up guys. I enjoyed your "imparting of knowledge"
in your exchanges.

George

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