searcy@bgsu-stu.UUCP (todd Searcy) (02/23/90)
Have anyone heard about a study put out by the M.I.T. Media Lab concerning people perception of HDTV? The study stated that relatively speaking, people can not tell the difference between HDTV and NTSC. Come o, be for real! I am doing a paper on onesde and perception of the quaility of the image on television sets. I know there have been many studies looking at theeffects of the VDT(computer workstation) and attitudes towards work. I`m interested in the home television receiver If you know of any research on this topic or anything that might be closely related could you pass it on? Thanks. I have seen HDTV and I`ve seen NTSC. Believe me there is a big difference. Or is there? :). Or is there? :) Thanks again. Searcy@barney.bgsu.edu
dave@imax.com (Dave Martindale) (02/27/90)
In article <5461@bgsu-stu.UUCP> searcy@bgsu-stu.UUCP (todd Searcy) writes: > > Have anyone heard about a study put out by the M.I.T. Media Lab >concerning people perception of HDTV? The study stated that relatively >speaking, people can not tell the difference between HDTV and NTSC. >I have seen HDTV and I`ve seen NTSC. Believe me there is a big difference. >Or is there? :). >Or is there? :) Thanks again. Searcy@barney.bgsu.edu There is a difference between NTSC and HDTV - if you sit close enough to the screen. NTSC television is intended to be viewed from a distance of about 10 times the picture height. At this distance, one scanline pair is about 1.5 arc minute high as seen from the viewer's eye - not bad, considering that the eye's resolution limit is around 1 arc minute. The horizontal luminance resolution is somewhat worse than this, and horizontal colour resolution again worse. Still, an off-the-air NTSC signal (or one from a video disc) displayed on a good NTSC monitor will look pretty close to sharp when viewed from 10 times the picture height. At that distance, a HDTV picture will appear wider, but not much sharper. However, HDTV is intended to allow you to view from about 3 times the picture height. At that distance, the resolution difference between HDTV and NTSC will be readily visible. (HDTV has only about twice the resolution of NTSC, so I can see where moving up to 5 times picture height is justified, but not 3 times). To really compare NTSC and HDTV side-by-side, you need to use an HDTV screen that is 2-3 times as large as the NTSC one, or place the HDTV screen a factor of 2 or 3 closer to the audience. You want to demonstrate how much larger an HDTV image can be and still retain acceptable sharpness, not that HDTV looks sharper at "normal" viewing distances. I've seen a NTSC vs. HDTV demo put on by the CBC that suffered from just this flaw. Both CRT's were located in the same plane, so the viewing distance was the same for both. The NTSC image was actually slightly larger than the HDTV one, and most of the audience was far enough away from the screens that the resolution difference was not very significant. In addition, the NTSC set was brighter than the HDTV one. Thus, it's not too surprising that I preferred the NTSC image half the time or more - not what the demo was intended to demonstrate, I'm sure. Dave Martindale
kassover@control.crd.ge.com (David Kassover) (02/27/90)
In article <1990Feb26.215623.9194@imax.com> dave@imax.com (Dave Martindale) writes: >In article <5461@bgsu-stu.UUCP> searcy@bgsu-stu.UUCP (todd Searcy) writes: > >There is a difference between NTSC and HDTV - if you sit close enough >to the screen. > I, for one, am not surprised. Long ago, in a galaxy far away, I was doing my Master's work in a project that involved IBM 3277 Graphics Attachments. They came in a variety of configurations, but we had the 14 inch screens and the 19 inch screens. The 19 inchers were wonderful, since what we mostly were dealing with were stroke graphics back then. You could turn out the lights and kick back and get your work done without hunching, etc... But the poor guys who had to work with projects that involved what we now call bitmap images went nuts, since the 19 inch screen had the same number of pixels (oops, it's IBM, therefore pels 8-) ) as the 14 inch. In order for these images to lose their perceived graininess, one had to move so far back that the subtended angle of the 19" screen was LESS than that of the 14" screen. I also notice, as I walk past rows upon rows of televisions in department stores that when I get far enough away from (most of) the big screen jobs to be comfortable watching them, the images are significantly crummier than comfortable viewing distance on smaller, "standard" CRT displays. The lesson I learned is that if you want to go significantly bigger, you have to provide both more and smaller pixels to retain perceive image quality. There's also a thresholding effect wrt brightness and contrast. I wonder if people in the pretty pictures graphics industry would benefit from a couple of good technical photography courses, where they go into the (mathematical) relationships between focal length, frame size, intended viewing distance, aspect ratios, etc.
katefans@world.std.com (Chris'n'Vickie of Kansas City) (03/01/90)
<1990Feb26.215623.9194@imax.com> dave@imax.com (Dave Martindale) writes: >> [...] >> NTSC television is intended to be viewed from a distance of about 10 >> times the picture height. [...] <2240@alfred.Teknowledge.COM>tbarnes@teknowledge.com (Terry A Barnes) > Is this true - I've read articles with varying ideal measures of how > far the eye should be from the screen - 5 times the diagonal, 8 times > the height (which is almost the same thing), 6 times the diagonal, etc. > Does anyone have a definitive answer? > > What are the effects of closer viewing - eye strain, visible scan lines, > what? I'm tempted to get a 30+ inch monitor when I upgrade, but what if > the couch is only 10 feet from the screen - would I be sorry I got a > "too big" screen? I don't have a definitive answer but I do have considerable personal experience with big TV's, as I live with a 6' x 8' Sony projector that I view from a distance of 12'. The vertical scan lines can be visible but are relatively unimportant compared to convergence, focus, linear response and chroma crawl. My opinion is that most of the eye strain and stress associated with normal TV viewing is due to the fact that you are looking directly at a light source. Projectors cast light on a screen and are no more stress causing than any film image on the same screen. Projectors can be sharper than any normal crt because of the lack of a shadow mask and the resulting RGB "triplets", purity problems and horizontal resolution limits. I find the 12" monitors on my graphics system to be more stressful in spite of the far higher resolution (and not just because they are at work :-)) In short, I don't believe that a TV can be "too big" and I want Hi-Definition very badly. These "experts" must be people who sit in the back row of theaters. Chris Williams katefans@world.std.com
pdy@sun.soe.clarkson.edu (P. D. Yapa) (03/16/90)
Last summer I was visted Japan. I went to Sony building in Ginza, Tokyo to just to see HDTV. They have a special room designated to show HDTV movies about every 2 hours. I should say the picture quality was exceptional. You can't even compare with NTSC / PAL /SECAM systems. I couldn't see any lines at all on a screen which was roughly 6 ft wide (guess). I went near the screen ( 6 inches from the screen). I still couldn't see any lines. you got to see to believe how good HDTV is.
mtv@milton.acs.washington.edu (David Schanen) (03/16/90)
For backwards compatability, why don't we just double the scan lines?
I don't know how the transmitters work but if we could use the existing
signal as part of the new signal, that would eliminate alot of expense.
-Davewave@mit-amt.MEDIA.MIT.EDU (Michael B. Johnson) (03/17/90)
(P. D. Yapa) writes: >>I should say the picture quality was exceptional. >>you got to see to believe how good HDTV is. I have to disagree. I have a 40" HDTV monitor and 1/2" Hi-Vision deck, and the image quality is nice, but I wouldn't say it would knock anybody's socks off. To me the most striking thing is the aspect ratio, which beats the hell out of NTSC, at least. Don't get me wrong, I'd rather record my animations on Hi-Vision than BetaCam, but it's not as good as it could (or should) be. Just my two cents. -- --> Michael B. Johnson --> MIT Media Lab -- Computer Graphics & Animation Group --> (617) 253-0663 -- wave@media-lab.media.mit.edu
sparks@corpane.UUCP (John Sparks) (03/20/90)
mtv@milton.acs.washington.edu (David Schanen) writes: > For backwards compatability, why don't we just double the scan lines? > I don't know how the transmitters work but if we could use the existing >signal as part of the new signal, that would eliminate alot of expense. > -Dave I think there has been some argument for this, but one problem is that while NTSC (US standard) is 525 lines (1150 doubled for HDTV) is not the same as PAL (European) which is 620 (somewhere around there). so doubling that would be 1240 lines. It would be a lot better if the world could agree to go to ONE standard HDTV rather than two (NTSC and PAL). So which do you support? PAL is used in more places than NTSC is. One compromise was to take a common multiple of both systems and use that. I have no idea where it stands now. But I hope they go with square pixels because I have a feeling that HDTV will become the new computer graphics standard also. -- John Sparks | D.I.S.K. 24hrs 1200bps. Accessable via Starlink (Louisville KY) sparks@corpane.UUCP <><><><><><><><><><><> D.I.S.K. ph:502/968-5401 thru -5406 A virtuous life is its own punishment.
toddpw@tybalt.caltech.edu (Todd P. Whitesel) (03/20/90)
sparks@corpane.UUCP (John Sparks) writes: > But I hope they go with square pixels >because I have a feeling that HDTV will become the new computer graphics >standard also. I doubt that. It would require them to define a screen width and height and a dot frequency IN ADDITION TO all the other parameters they are already arguing over. Computer graphics are hard to broadcast via radio because of transmission bandwidth restrictions that force you to trade between quality and cost in a major way. The standard should be designed with graphics in mind but don't expect them to broadcast 24 bit megapixel to the mass public any time soon. Wait until we have fiber optic cable everywhere. Todd Whitesel toddpw @ tybalt.caltech.edu
billd@fps.com (Bill Davidson) (03/21/90)
sparks@corpane.UUCP (John Sparks) writes: > But I hope they go with square pixels >because I have a feeling that HDTV will become the new computer graphics >standard also. In article <1990Mar20.120112.4942@spectre.ccsf.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: >I doubt that. It would require them to define a screen width and height >and a dot frequency IN ADDITION TO all the other parameters they are already >arguing over. Yep. Wouldn't it be great? You could actually have expectations for the edge of the picture. Heck, you might even get to see the whole image! What a novel idea. The edges of movies could actually be seen! The width and height don't need to be defined but their ratio to each other does. This isn't even just a computer graphics issue. One of the things that really pisses me off about current consumer televisions is they don't show the entire signal. They cut off the top, bottom and sides a bit. HDTV should define the number of pixels that are shown (all of them dammit!). They should be square and the same number should be shown on all monitors. Don't give me any crybaby excuses that it's hard to do. It needs to be done. The bandwidth problem is real but we can probably live with less channels and we don't really need digital rgb. If we can just do color a lot better than NTSC I'll be happy. I don't care if HDTV's are expensive at first. We real vidiots will pay for it. As it becomes more commonly available, it will get cheaper. --Bill
martys@mchale.ism.isc.com (Marty Stewart) (03/21/90)
I am writing a 20-page research paper for school on HDTV and its influences on the world market. I am looking for articles, books that will give me some insight into the Japanese's role with HDTV and where they want to market it, the European Community's standard of HDTV and if they plan on letting other countries into their market and the U.S.'s late start into the HDTV industry. I know that the U.S. is further behind in the HDTV technology and that it is of concern to the Defense Dept. as well as the television industry. I would like to fit into my paper each nation's view (first world, second world and third world countries) on where HDTV is going and whether they want to be in on it, etc. Any leads on articles would be appreciated. Send mail to me. Thanks. martys@ism.isc.com
peter@celia.UUCP (Peter Farson) (03/21/90)
In article <1902@mit-amt.MEDIA.MIT.EDU> wave@media-lab.media.mit.edu (Michael B. Johnson) writes: >(P. D. Yapa) writes: >I have to disagree. I have a 40" HDTV monitor and 1/2" Hi-Vision deck, and the >image quality is nice, but I wouldn't say it would knock anybody's socks off. > ....... I've seen a few HDTV video displays, and the one thing I find disappointing about them is that they are interlaced. Interlacing adds a buzzy quality that prevents a still image from looking truly still, as it does on a hires non-interlaced monitor. -- The flesh of animals who feed | Peter Farson - Rhythm & Hues, Inc. excursively is allowed to have | celia!peter@usc.edu a higher flavour than that of | celia!peter@tis.llnl.gov those who are cooped up. - Samuel Johnson |