HD resolution is not very important. At normal viewing distances, most people cannot make out HD resolution, even on a 42-inch screen. What is important is sharpness, according to engineer, educator and consultant Mark Schubin, author of Mark's Monday Memo. Speaking to public TV engineers recently just prior to NAB, Schubin reminded engineers that sharpness is proportional to the square of the area under an MTF curve (one plotting contrast against detail fineness).
"HD lenses and HD cameras increase the area under the curve at almost all resolutions, so HD looks better even on a six-hour mode analog VHS recording," he reiterated later for HD Notebook. "MTF curves are affected by lenses, cameras and filters, so it's important to shoot HD. They are not affected by recording or distribution that does not involve filtering. So if you've shot in HD and downconverted, that's as bad as it's going to get (not counting compression artifacts). If you look at the MTF curves for SD and HD and if you cut off resolution at SD levels, all you lose is the area under the 'toe' of the curve, which is practically nothing. So, while you lose a tremendous amount of resolution in downconversion, you lose practically no sharpness," he said.
Schubin also said that all major manufacturers have used this sharpness vs. resolution principle in their recorders--pointing out that HDCAM, in reality, records only 1,440 pixels horizontally instead of 1,920 (and only 480 in chroma). DVCPRO HD and D9HD record only 1,280 (and 640 chroma)--in 1080i. Schubin also told the PBS tech meeting in Las Vegas that it's important to start shooting in HD as soon as stations can afford the necessary cameras and lenses, and that "it's vitally important for all broadcasters to transmit DTT" (digital terrestrial TV) and to maximize their respective coverage areas.
