IMAX computing - #26

Daniel Rutter believes that if you don't think really big screens are really cool then you might perhaps have mistaken this magazine for another one. The embroidery mags are on the other side of the newsstand. There you go. Glad to help.

Every true geek can appreciate the niftiness of really big screens.

Quite a few of us have even managed to figure out why it is that a one-metre-diagonal screen four metres away looks better than a 50cm-diagonal screen two metres away, even though they both take up the same portion of one's field of view.

Bigger screens further away make it easier to look at the image, rather than the screen, you see. Scratches and dust and phosphor lines and aperture grille damper wires are harder to see when the screen's further away. And your eyes are more relaxed when they're focusing closer to infinity. And, of course, more people can watch a bigger screen at once, without having to peer at it from extreme angles, or all sit on each other's lap.
Giant screens, however, are pigs to live with.

Giant CRT TVs are very big, very heavy, and pretty darn expensive. Rear projection sets can have bigger screens and are cheaper and lighter, but they're fairly delicate, have a lousier picture than CRT, and have cabinets you could park a blimp in.

Plasma screens don't eat all of your floor space, but they are not cheap, and their resolution is far from thrilling. A $10,000 16:9 46-inch plasma screen is only likely to give you 853 by 480 pixels, which is little better than a CRT TV with similar screen dimensions.

So, say I, the heck with that. If you have a mere few thousand bucks eating a hole in your pocket and a hankerin' for giant screen fun, get yourself a video projector.

Liquid Crystal Display (LCD) or Digital Light Processing (DLP), for preference; older three-lens Cathode Ray Tube (CRT) projectors give nice results for video, but they're big and heavy and generally rather dim, and they need regular tweaking to keep the three guns lined up. LCDs and DLPs can be small and neat (even a big one is likely to be a one-man carry), and 1,024 by 768 (or better) models are easy to find.

Some people say that projectors are for serious home theatre enthusiasts only. Their reasoning is simple enough: projectors are, indeed, not much good for ordinary TV watching or computer use, because you have to dim the lights to get a decent picture.

It's now easy to find impressively bright and highly portable LCD or DLP projectors for the price of a high-end CRT TV, but even a 1,000-plus ANSI lumen projector can only throw light, not darkness, so the darkest black a front-projected image can possibly contain is the same as the un-illuminated colour of the screen.

In a room lit brightly enough that you can read a newspaper, no screen's going to be very dark. This means washed-out viewing -- not as good as the results from even a basic rear-projection TV.

Far as I can see, though, this just means you'll need to buy a TV too. Big deal. Drop $300 on an undistinguished-brand 50cm set. Use that for any viewing where a giant attention-commanding display isn't called for -- do you really want to see a whimsical weatherman larger than life sized?

When you want movies or sport or Hegemonia or a Winamp plugin on the big screen, draw the blinds, dim the lights, and whip out the projector from behind the couch. Or take it to someone else's house. Portability is a big plus for projectors.

You don't need much besides the projector, either. A screen to project onto, yes, but if you have a good slab of white wall (or, for party purposes, ceiling...) handy, that'll do. A cheap second-hand roll-up slide projector screen will give you better results.
For everyday computing and competitive gaming, projectors are a rather perverse choice. Consumables pricing isn't a problem: one few-hundred-dollar lamp every few thousand hours of run time isn't bad. The problem is that a really big display isn't practical to use, because you have to look around it all the time.

You do that anyway, even with an ordinary computer monitor: the central high-resolution spot in your field of view is only about three degrees across, horizontally. Even a plain 17in PC monitor would have to be about six and a half metres away for it to occupy only three horizontal degrees of your field of view. To get the impression of a sharp view of a whole screen at normal distances, therefore, your eyes dart around as necessary. That's how human vision works. But if the display's ultra-hyper-gigantic, you have to move your whole head.

If you don't see too well then a vast display can be great, and it'll certainly put you right in the middle of your games. If you have normal eyesight, though, then doing word processing on your wall is just weird. And if you have to move your head to see the whole screen in a game, you're unlikely to deliver your best performance.

Practicality's not what giant displays are about, though. They're about warming the cockles of your geekly heart. That's what they're about.

And that, I think you'll agree, is enough.