At 2:32 PM -0500 1/11/07, Manfredi, Albert E wrote:
But HDTV is considerably sharper than any of these. Whether or not actual receivers can make complete use of what's available, HDTV video bandwidths are out in the 20-30 MHz region.
Yeah right...Virtually all HDTV gear is operating at a fraction of this bandwidth. Sony rolls off most everything that is above 20 MHz. And then that video hits a brick wall in the MPEG-2 encoder. The actual delivered frequency response is probably below 15 MHz when all encoding and transmission losses are accounted for. And that's the best case, when the picture is not compromised by quantization errors and blocking artifacts.
1080 at 60i or 1080 at 30p is 960 cycles/line * 1080 lines/frame * 30 frames/sec = 31.1 MHz. 720 at 60p is 640 cycles/line * 720 lines/frame * 60 frames/sec = 27.6 MHz. I submit, a major difference between any analog scheme and HDTV.
One more thing Bert. The major reason for the long term success of NTSC and PAL is that they were able to deliver most of the image detail that is important to the human visual system. Did you look at the Wizard of Oz image that Cliff posted. The grain in that image came from the film, not the TV system. The real issue that HDTV solves, is the ability to display a TV image on a MUCH larger screen and still have it look sharp. On displays that are less than 40 inch diagonal, most of the extra resolution in an HDTV signal is wasted.
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