Lileks on HDTV

Last Friday’s Bleat by James Lileks records his observations on receiving high definition TV. Nice piece, as usual, but some technical corrections are in order. He says:

Normal TV has something like 440 lines on the screen. (Or 380. Or 400. Cursory google search leads me to baffling videophile sites I haven’t the patience to wade through.) DVDs have about 800 lines. (See parenthetical note to previous sentence.) They’re better. HDTV has 1081 lines.

I suspect that there is a widespread confusion about TV resolution because this has always been measured in terms of ‘lines’. But there are at least two kinds of lines on a TV screen: horizontal ones and vertical ones. The number of discernible horizontal lines of resolution equates to the vertical resolution in pixels; and the number of discernible vertical lines is the horizontal resolution in pixels. So here’s a primer on what resolution you can expect from various signals:

Name Horizontal resolution
(number of vertical lines able to be
visually distinguished across the
width of the display)
Vertical resolution
US Analogue TV (NTSC) ~400 480
Australian (and European and Indian) Analogue TV (PAL) ~400 576
US VHS VCR ~200-250 480
Australian (etc) VHS VCR ~200-250 576
US DVD with analogue connection ~500-550 480
Australian (etc) DVD with analogue connection ~500-550 576
US DVD with digital (DVI/HDMI) connection 720 480
Australian (etc) DVD with digital (DVI/HDMI) connection 720 576
High definition TV (US and Australian) 1,280 720
High definition TV (US and Australian) 1,920 1,080

In the case of the HD signals, the actual visible resolution depends largely on the display device. There are few, if any, devices available yet that actually support all 1,920 horizontal pixels, even if they can pull off the 1,080 vertical pixels. This will change soon, though.

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