J. Stephen McDonald |
May 31st, 2005 09:03 PM |
Quote:
Originally Posted by Michael Best
Why does SD footage look so bad on an HDTV monitor?
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After reading numerous messages on several discussion forums about the performance of various HDTV monitors, one thing is apparent: Some makes and models display SD sources very well and some do so poorly. Before I purchased an HDTV last year, I spent some time checking out every model I could. How well they displayed SD was given equal importance to their HD picture quality. After I spent two months annoying all the local sales people, I narrowed it down to CRTs by Sony, Panasonic and JVC. I finally chose a JVC AV-30W585. It did the best job with SD sources. It converts every input to 1080i (although none of the current consumer HD monitors actually can resolve that many lines on their screens). It makes even mediocre SD inputs look better than they would on a good SD monitor. However, I can't use it for DV editing, as it makes the footage look too good and I can't judge it properly. I have to use an SD monitor for that purpose.
This JVC has a cinema-expansion mode, that zooms the 4:3 picture to full 16:9, without distortion, although some of the image is lost at top and bottom. My DV footage still looks very sharp when expanded like this on the 30W585 and can pass as a poor man's HDTV source. I've used a resolution chart with my VX2100 to measure the sharpness of the expanded SD picture on this monitor. Even though only about 75% of the original scanning lines of the 4:3 recording mode contribute to the 16:9 picture, it shows an apparent horizontal resolution of about 450 lines. The vertical resolution seems to actually be higher than the 480 lines of an NTSC display in SD. This is due in part to the excellent computerized line restructuring system of the JVC HD monitor in upshifting to 1080i.
Although the clipping of the top and bottom of the image and then expanding it, primarily reduces the vertical resolution, it seems that the horizontal res is also lowered by the expansion. When the picture is expanded to 16:9, only about 385 scanning lines of the original 480 are used, dropping the vertical res a noticable amount when viewed on an SD widescreen monitor. However, the horizontal res you could see on an SD widescreen is also reduced by this clipping and expansion as the pixel points that existed on the original source are farther apart on each line. But, the upshift restructuring of this JVC HDTV restores a good deal of both measures of apparent resolution, that would otherwise be lost.
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