Home cinema - Revised! 35-37 inch HD telly recomendation!

Slurp wrote:
wrote in message
oups.com...
Slurp wrote:
Assuming an average eye resolving angle of 0.03 degrees, and assuming a
widescreen 16:9 image with a horizontal resolution of 1920 pixels,and
using
H.264 compression (MPEG4 with 8x8cell compression) the following optimum
screen sizes apply. (by optimum I mean the pixel size is *just* on the
limit
of being resolved by the eye, i.e. any closer to the screen and you will
start to see jaggies and motion artifacts).

Screen size(inch) 17 21 28 32 36 42 50 80
ViewDist(m) 3 3.6 4.8 5.4 6.3 7.5 9
14.1

Following this through for SD (where the pixel width is more than
double), you are suggesting that I should sit over 10m away from my 28"
TV?!

If you don't want to see any motion artefacts, then, assuming you have
perfect vision - YUP!

Just shows you how crap digital TV is - for analogue transmissions you can
use the rule of thumb optimal view distance of 6 * picture height.

You set the limit as 1 pixel matching the resolving angle of the eye.
You suggested sitting any closer would not be acceptable. You mentioned
MPEG-4 encoding, but didn't include it in your calculation.

I showed how silly this was by applying your reasoning to SD
transmissions (giving my TV a minimum viewing distance of 10m - clearly
stupid!).

Now you claim it's to do with digital vs analogue. Rubbish! 6 * picture
height _is_ a reasonable rule of thumb, but it gives 1/5th the viewing
distance your original calculation suggests, even before we factor in
the slightly/greatly (depends on decoding) lower horizontal resolution
of a composite analogue signal.

In other words, the often quoted 6H for SD and 3H for HD are reasonable
- your original figures were not.

The reason is that human viewers are more than happy to view images
where the resolution is lower than the resolving angle of the eye, and
this is especially true with moving images.

Of course, you made need to sit in the next room or house or even
street before MPEG-2 compression artefacts become invisible, but that
is a different calculation entirely!

Cheers,
David.