[opendtv] Re: News: If There's a High-Definition TV in Your Future, Wait Till After the Holidays

At 2:40 PM -0400 8/27/07, Manfredi, Albert E wrote:

Craig Birkmaier wrote:


 Lot's of interesting data points in this story.

 Of particular interest:

 According to the research firm iSuppli, the average retail price
 of 42-inch HDTVs - one of the most popular sizes this year - has
 declined to $1,522 from $1,844 last Christmas, an 18 percent
 drop.

 (Note: 42" sets have the ability to deliver resolution
 approximately equal to 480P, which is well matched to standard
 definition DVD).


42" sets start to appear smallish in huge stores like Best Buy or
Costco. But in a typical den or living room, they are quite huge.

Let's do some realistic numbers. The screen of a 42" 16:9 set is 20.66"
high. If we watch the TV at 5 picture heights viewing distance, that's
8.6' away. So I think that's a realistic sitting position in may rooms.
Almost 9'. Some would say that's too generous.

Human vision corrected, if necessary, to 20/20, should be capable of
perceiving 1 arcmin of angular separation:

http://en.wikipedia.org/wiki/Visual_acuity

http://www.ndt-ed.org/EducationResources/CommunityCollege/PenetrantTest/
Introduction/visualacuity.htm

http://webvision.med.utah.edu/KallSpatial.html

Assuming the model is this simple, which I don't think it is, what does
an SD, ED, and HD set with 42" screen offer, if viewed from this 8.6'
distance?

SD 480i (or 312 effective): 2.2 arcmin. Obviously, this can be improved.
(Interlace factor 0.65.)

ED 480p: 1.43 arcmin. This can also be improved.

HD 720p: 0.95 arcmin. Just barely over the limit.

HD at 1080i (or 702 effective): 0.98 arcmin. Almost identical to 720p.

HD at 1080p: 0.64 arcmin. Overkill. But now you can move in to 3.5
picture heights, or 6' viewing distance for a 42" set, and now you will
be right at 0.91 arcmin. Just about right. Slight overkill.

So, a 42" HD set should be good for viewers who do not live in a
McMansion.
Your figures are slightly more optimistic than those I calculated in 1992 - but they are well within the range of acuity for some of the population.
40 inch diagonal is right at the transition point where 720P begins to provide additional detail. If the viewer is willing to sit inside the five picture heights you used as the designed viewing distance they will see the additional detail. At five picture heights it's a crap shoot. Some viewers will see the added detail some won't. The added resolution of an HD disc format will be minimal at best.
All of this is subjective. One can look at all the panels on the wall and see significant differences in displays of the same size.
Other factors that have an impact are contrast ratio, brightness, and the internal video processing circuits that scale the source to the actual screen resolution. Most sets remove some of the detail in progressive source and much more for interlaced source due to the de-interlacing techniques that are used. 



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