Interesting topic, vertical resolution. Don't see much discussion of it online, perhaps with the exception of the OpenDTV forum at Topica.com.
Earlier in this section I posted a simplified table showing measured vertical resolution results obtained during the mid-1990s approval of ATSC HDTV. There was a difference of opinion about how relevant these data were today. But if someone has newer independent data, or can detail what's happening with 720p/1080i broadcasts currently that makes this data not relevant, please post the information. (Seems to me that U.S. broadcasters haven't yet reached the resolutions achieved during these approval tests by the FCC's experts committee. Expressed my 2 cents why I think this is so just
yesterday , so no need to repeat it.)
But, going to the original query, the measured results with a 5-rpm test pattern indicated vertical resolution at 1080i was 400 lines and for 720p it was 420 lines. The committee provided some notes about vertical resolution below its
table 2.3 . My assumption would be that vertical resolution at 1080i would drop to 400 only within the rotating test pattern, and that vertical resolution would increase (to 800 lines static) as the test pattern rotation slowed.
Would vertical resolution be significantly different with video motion from film originally captured at 24p or video taped at 60i (60 interlaced fields per second)? Wouldn't think it would match a simple rotating test pattern, but regardless of the original source our eyes are blending two 1/60-sec fields into 1/30-sec frames with 1080i. I'd think vertical resolution reductions would be similar to those obtained in the ATSC tests.
This
recent post outlines why vertical resolution is deliberately reduced (smeared) to prevent interline flicker. Combined with a Kell factor of ~0.7 (times the scan lines) this accounts for the drop in actual resolution as opposed to scan lines. Oversampling is sometimes mentioned as an aid to boosting resolution (h and v). With oversampling, after standard filtering that gives you greater resolution. But does anyone have any reliable information on how much HBO, NBC, and ABC may be oversampling? -- John