[opendtv] Re: 1080p @ 60 is Next?

  • From: Tom Barry <trbarry@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Thu, 17 May 2007 12:27:57 -0400



Craig Birkmaier wrote:
> Olivier is correct about the 30 degree field in terms of the immersion
> effect. But there is more. I can sit at a high resolution computer
> display (say a 30" Apple cinema display that exceeds 1080P resolution)
> so that it covers 30degrees of my viewing field. Unfortunately at this
> close viewing distance the immersion effect does not work. We typically
> need a really big display viewed at a distance greater than 15 feet for
> it to work properly.

Craig -

Can you provide a reference for that 15' number? It seems about twice what I would have guessed.

- Tom

At 1:41 AM +0200 5/17/07, Olivier Houot wrote:

John Shutt wrote :

----- Original Message ----- From: "Olivier Houot" <olho_avatar_i@xxxxxxxxxx>


The 1080 format is designed to be close to the eye resolution limit under a 30 ° angle which means we should be able to perceive the increased sharpness.



Based on what? An arbitrary screen size viewed at an arbitrary distance?


I probably don't get your meaning,but...

An average 1/60 of a degree angular resolution for the eye, means 1800 horizontal pixels for a 30 ° viewing angle. With some margin and the choice of a 16/9 aspect ratio we get the 1920x1080 format. The angle provides a fixed ratio between screen width and distance, so there is only one arbitrary parameter left. If you choose the screen size as the variable, then studies show that for psychological confort it is not so arbitrary as you need to set it to a big value, but still within "acceptable" limits for the famous "average" home.

The 30° value itself was a result of NHK studies showing it as lower limit for a sense of immersion to kick in.


The average of 1/60 of a degree angular resolution for the eye is well beyond the limits of human perception for most viewers - i.e. 30 cycles per degree. Under the correct circumstances - i.e. very high contrast, or a temporal element, most of us can perceive details at this level, however, on average, 22 CPD is adequate to deliver what is perceived as a sharp image.

Olivier is correct about the 30 degree field in terms of the immersion effect. But there is more. I can sit at a high resolution computer display (say a 30" Apple cinema display that exceeds 1080P resolution) so that it covers 30degrees of my viewing field. Unfortunately at this close viewing distance the immersion effect does not work. We typically need a really big display viewed at a distance greater than 15 feet for it to work properly.

Regards
Craig


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Tom Barry                  trbarry@xxxxxxxxxxx  




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