On Sun, 11 Aug 2002 00:38:36 GMT, "David McCall"
>
>"Neuman - Ruether"
news:3d5b6b7b.8666236@newsstand.cit.cornell.edu...
>> On 9 Aug 2002 13:13:16 -0700, nyc11370@yahoo.com (nyc11370)
>> wrote:
>>
>> >Progressive scan CCD video capture (30 full frames per second) is a
>> >feature that I think all DV camcorders should have it.
>> >
>> >The main reasons for progressive scan CCD (30FPS) capture:
>> >
>> >(1) 30FPS PS better than interlaced video and is sufficient for human
>> >eyes. I don't understanding why people claimed 30FPS is not smooth,
>> >are they sure what they are talking about ? Movies are at 24FPS (or 48
>> >dual frames) and people don't find any problem watching it. Obvious,
>> >these people never saw a progressive TV or compared progressive TV vs.
>> >interlaced TV. The interlaced scan lines on a traditional TV flickers
>> >so much and your eyes get tire in shorter time.
>> >Samples:
>> >http://home.nyc.rr.com/hitechproducts/interlaced_tv.jpg
>> >http://home.nyc.rr.com/hitechproducts/progressive_tv.jpg
>> >
>(1) AFAIK nobody in this group has seen a progresive scan "TV".
>There are Projectors with progresive scan capabilities. Perhaps
>that is what he means.
>
>Motion pictures are not shot in progressive scan. In fact they
>are not scanned when displayed. They are displayed just
>as if they were slides. Film projectors need a bit of time to pull
>down the next frame, which causes a flicker to the image, but
>if the flicker is fast enough, the eye won't conciously notice it.
>So, the show each frame mor than once to increase the flicker
>rate. DLP and LCD projectors can change from one frame to
>the next frame so fast that there is no perceptable flicker, and
>these projectors also display the whole frame at once.
>
>I have no idea what those links are about, but they certainly aren't
>comparing apples to apples. I think it is about marketing people
>trying to sell progressive scan TVs. In any event. Stills will never
>show you the advantage of interlaced scan.
>
>The flicker rate of any given TV will still be the same, reguardless
>of the style of scan that was used for aqusition. In fact most "video"
>recording devices still store the image as 2 fields, even if the CCD
>captured the entire frame at the same time.
>
>As far as motion is concerned, NTSC video is efectively 60
>frames per second. First he claims that 30 frames would not
>show "flicker, but the flicker he is complaining about is efectively
>at 30 frames per second, by his definition.
>
>> >(2) You get double resolution with progressive capture and playback.
>> >NTSC progressive scan is 480 filled lines per 1/30S vs. 240 alternated
>> >scan lines + alternated empty lines per 1/60S.
>> >
>(2) If your scan rate was 60 full frames per second this would
>be true. However, progressive scan at a rate of 30 per second
>has exactly the same amount of image lines as an interlaced
>image (2 fields per second). Guess what. If you were to display
>a 30 frame per second progressive on a "TV" it efectively
>becomes interlaced becaus the TV only displays half of it at
>a pass. You would have to use a true progressive display
>device to get the improvement he suggest, and very few viewers
>have this capability at home.
>
>> >(3) More people are releasing their videos on the Internet. Computer
>> >displays are progressive. Most digital formats on PC are able to play
>> >30FPS, progressive - both fields: odd and even lines. When you play
>> >back a interlaced file on computer as 30FPS without properly
>> >de-interlacing, you can see the scan lines due to the time lag between
>> >odd & even lines when the image is moving.
>> >Samples:
>> >http://home.nyc.rr.com/hitechproducts/interlaced_dv.jpg
>> >http://home.nyc.rr.com/hitechproducts/progressive_dv.jpg
>> >
>(3) Computer displays are not all progressive, but the all run at
>a higher scan rate than conventional TV. The closest to a normal
>TV rate is 60 full frames per second (although most people run
>them at a higher rate to reduce flicker. This is not why conventional
>video does not look right on a computer though. It is because most
>software completely ignores that the video is interlaced, and displas
>both fields simultaniously (instead of sequentially). Plus, I am not
>aware of any computer software that makes any attempt to
>synchronize the video frame rate to the computers frame rate,
>or visa versa. Again, his samples have no direct bearing on the
>topic of discusion here. The modicum of truth here is that
>progressive scan does look better on a computer than interlaced
>video currently does in the same invironment. If a computer or other
>non interlaced (or high scan rate like a computer) is to be your
>primary display device.
>
>The way film gets away with a slower frame rate is by using a
>longer exposure rate, per frame, than video does and thus blurs
>out any motion. To me, blurinr the image does not make it sharper.
>When video aqusition was done with tubes it was truly scanned.
>That means that any part of the image is only exposed for the
>amount of time that it takes for the "electron beam" to scan over it.
>this makes for a very high "effective" shutter rate, even though it
>only cross that part of the image 30 times a second. If TV had been
>designed to display by scanning at a mere 30 full frames per second
>the motion would be horendous. Today's technology (CCDs) eliminates
>this issue, because the whole frame can be exposed at the same
>time, and the "shutter rate" can be just about any thing you could desire.
>The shortcomming is that most people still watch TV on TVs and they
>are all 60 fields per second (at least in NTSC land.
>
>Another problem with low frame rates is that you have to know a
>lot more to shoot it correctly. At 60 fields the motion apears smooth
>even if your subject is moving very fast, but at half that rate motion
>becomes very jittery if you don't take this into account. Fast pans
>only work with long effective shutter rates to blur them out. Wheels
>strobe and seem to run backwards sometimes. fast moving subjects
>will blur unless trhe camera tracks the motion, or the motion is
>moving toward or away from the camera.
>
>> >(4) Progressive DV contents will be playback correctly on analog
>> >interlaced TV. It will be playback as normal interlaced signal without
>> >any problems.
>> >
>(4) See above. Motion will only be acceptable if you use relatively
>long shutter rates.
>
>> >(5) The reason of interlaced video is because the analog NTSC is
>> >limited to 6Mbps bandwidth and the original TV can only handle half of
>> >the resolution at a time.
>> >
>(5) I would hesitate to say that the original decision had anything to
>do with Megabits per second of band width. In fact I doubt anybody
>knew what a bit was 80 years ago :-) But bandwith did enter into it.
>Megahertz was the measure, ant I think the number was 5mhz,
>but don't quote me on that one without checking. It also had to do
>with the available technology and cost factors as well. Plus some
>of the stuff mentioned earlier.
>
>> >(6) The TV world is moving to progressive. New technology such as
>> >HDTV, progressive DVD, TV displays computer signal and etc...
>> >
>(6) There is some truth to this one, but it has more to do with
>conforming to the, even older, motion picture standard
>(which was also based on technological and cost limitations,
>more so than aestetics). Some of us aren't too happy to se
>this trend, but wat are you going to do. The motion picture folks
>have a lot of influence. Thats why we have copy protection, and
>partially why it has taken so long to get DVD-Rs into the
>consumer marketplace.
>
>> >Sony VX2000 is one of the best DV cams, I hope SONY will add the 30FPS
>> >progressive capture in their upcoming model.
>> >
>This last, unnumbered item is OK. The VX-2000 is a very nice
>consumer camcorder, and 30 progressive is better for people
>that are shooting for computer/web based applications.
>
>David
>
>> >Gary
>>
>> Uhhhhh....., well...., yuh got the
>> last part right, anyway......;-)
>> David Ruether
>>
>I'm with you, David. I think we could nominate this one
>for the "Most mis-information in a single post" award :-)
>
>