[opendtv] Re: Gateway launches 30-in. "Extreme HD" 1600p display

  • From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 10 Oct 2007 16:48:33 -0400

Mark A. Aitken wrote:
From what (little) I know, 1000:1 is smaller than 10,000:1, but higher than what may sometimes be the 'usual' of 5:1..

(from Mark Schubin..."...Under typical home-TV viewing conditions, no TV screen delivers contrast ratios anywhere near 10,000:1. 5:1 is probably not unusual...")

Now, I know this is taken out of context, and I know that Mark will (most likely) not LIKE that I have pulled this out of its context,
No objection at all. If we define contrast ratio as the quantity (desired light + undesired light) divided by undesired light, and we say that a display has a high-level luminous emittance of 100 ft. lamberts and ambient lighting in a room with lights on is about 25 ft. candles, then, depending on reflectance, we have roughly (100+25)/25 or 5:1. If the TV were five times brighter and the room five times darker, we'd be at 505/5 or 101:1. Getting to 1000:1 is possible, but probably not with any lights on. Getting to 10,000:1 would probably be impossible even in a home environment with all lights out and black-velvet walls; the light emitted from the display would bounce off the velvet sufficiently to screw up the contrast ratio.

As for your later argument on resolution, from a strictly resolution perspective, I also concur wholeheartedly. Although the limiting resolution of the eye is great (else we couldn't see stars at night), it requires tremendous contrast ratio (the light of a sun against the blackness of space). The familiar eye-doctor E chart (a Snellen chart) is based on human ability to perceive no more than one arc-minute of resolution, and that's going from the black to the white of the Snellen chart. For reference, a 480-line 25-inch 4:3 display viewed at nine feet has a maximum resolution of almost exactly one arc minute.

All of that being said, humans don't respond psychologically to resolution; we respond to sharpness, which Otto Schade showed is proportion to the square of the area under a curve plotting contrast ratio against resolution (the familiar MTF curve). If a display's resolution, even if it's imperceptible to a viewer, enables higher contrast at perceptible resolutions, then that display will look sharper than one that doesn't, even if the viewer can't perceive even SDTV resolution. That's why stuff shot in HDTV looks sharper even when viewed from a six-hour analog VHS recording.

TTFN,
Mark
(a different one)



----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: