Digital TV

An interesting quotation from this week’s New Scientist confirms what I’ve suspected* for a while:

The latest 42 inch widescreen flat plasma panel screens cost around $7000, not counting a $250 wall mount and the digital tuner needed to receive broadcasts. Yet customers appear unconvinced of their quality. It turns out you cannot see the difference between a 500 and 1000 line display if you are more than six times as far from the screen as its height. A 42 inch display is less than 60 centimetres high, which means you don’t notice the difference across a 4 metre room.

This of course makes sense – the eye doesn’t have unlimited resolution. In fact, even in the fovea (the region of the eye with the most photoreceptors) it isn’t *that* high.

I remember when I saw a high definition TV at a museum in the US; I was duly impressed with the picture quality, but I did think that it didn’t look all that much better than a DVD quality image on a PAL TV (625 lines, no less). Big TVs are perfectly good, and there’s a real justification for flat TVs. But the vast majority of people certainly don’t need ultra high resolution TVs if they’re going to be used for ‘lean back’ viewing (as opposed to, say, computer work).

* I could have worked all of this out myself ages ago given the density of photoreceptors in the fovea and a bit of paper, but I never got around to doing it. Oh well.

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