[opendtv] HD vs. 625 vs. 525 vs. 405

  • From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 27 Aug 2004 18:32:05 -0400

Having just returned from a shoot in New Zealand, I thought I'd throw my 
two cents in on this.

Back in the early 1950s, a U.S. delegation toured UK TV facilities to 
try to determine why UK pictures looked better.  At the time, the UK was 
405 lines, not 625, but it was still said to have better pictures.  The 
delegation determined it was because the UK equipment was better 
maintained -- clean lenses, etc.

I found the same in New Zealand.  The equipment was in impeccable shape.

Food for thought:

- The resolution of human vision tops out at about 30 cycles per degree, 
nominally about 22.

- U.S. viewers sit about 9 feet from their TV sets (the Lechner distance).

- Those two facts combine to make it impossible for viewers to see more 
than 480 lines on a 25-inch 4:3 TV at normal viewing distance.  If it's 
22 cpd and 16:9, it's no more than 480 lines on a 42-inch set.

- Meanwhile, because the psychological sensation of "sharpness" is 
proportional to the square of the area under an MTF curve and the use of 
HD in production leads to a higher MTF curve at all detail resolutions, 
a viewer watching a non-HD set will nevertheless see an improvement in 
sharpness from HD-shot programming.


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