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.