Black Screen Saver for OS X Leopard. No Downloads Required.
My wife has a new computer, an Apple 24 inch Aluminum iMac. The screen on it is beautiful. It's brighter and has a much better range of viewing angles than my 20" Aluminum iMac (which display is pretty awful compared to the wonderful display in my old white 20" iMac that the Aluminum was supposed to replace.)
My wife's computer lives in the living room of our house. She likes to have it there so that she can be around her family while doing bills, working on video transfers, and so on.
This is the same room of our house that our TV resides in.
When we're watching a movie on the TV, that big, beautiful screen is serious competition for the TV. Annoyingly so. On her old computer, my wife had a standard screensaver for the system that would turn the screen black. That option was not provided on her new computer. On the old computer, the monitor was a separate piece of equipment from the computer itself. So the monitor could be switched off, if need be, while the computer was still running, perhaps encoding a video for writing to DVD. The iMac is all one thing. There's no separate power switch for the display.
Well, in fact there are ways of making the screen go black on the iMac. But they weren't obvious to us when we were preparing to sit down to a movie last night with the evening slipping away while we were fussing with a computer instead of starting the film.
What we expected to find was a screen saver in the Screen Saver section of System Preferences that would simply make the screen black. What we didn't find (mind you, we're not Mac novices around here) was the "Put the display to sleep" option under Energy Saver that would have done pretty much what we wanted--except that it can't simply be activated on demand, like a screen saver. (And exactly how one activates a screen saver on demand on a plain-jane Mac is yet another issue.)
An internet search turned up the Basic Black screen saver. It's donationware and I wish them all the luck in the world. It does exactly what's wanted. How much it's worth to someone should have nothing to do with the fact that we're talking five minutes with Quartz Composer, tops, to make the thing. It's like the old joke about the auto mechanic's bill presented after tapping on the car's engine to make a problem go away: $1.00 for the tap, $99 for knowing where to tap.
There are a couple of Quartz Compositions already on the Mac that can fill the bill.
They're in the Macintosh HD/System/Library/Compositions folder on a standard Leopard install.
Monochrome.qtz turns my screen black. I haven't looked at the QC script to see that it does it in all instances, but it seems to do so.
XRay.qtz turns the screen black with some very brief, and very subtle, flashes of dim, dim light every so often. The flashes are dim enough that they could easily pass unnoticed in normal lighting.
To make these available to Screen Saver in System Preferences, use Finder to copy these files from Macintosh HD/System/Library/Compositions to Macintosh HD/Library/Screen Savers. Then they will be available under the "Others" section at the bottom of the screen saver menu. They could also be placed in Macintosh HD/System/Library/Screen Savers but they might be lost through an OS update (though I would tend to doubt it.)
You know that picture you've got in iPhoto of the inside of your camera's lens cap? The one labelled "Black Bats in Coalmine at Night During New Moon"? You can use it as a black screen saver, too. We didn't have ours available last night. So we ended up turning the iMac around so that the screen wasn't facing us during the movie.
Not what I expect to have to do with a Mac, I can tell you.
I took a look at Monochrome.qtz. It'll show black for you. It wants an input image to convert to a monochrome image. No image, it stays black. It's overkill versus an even simpler Quartz Composer script to just show black, but hey, it does the job as-is and all you've got to do is copy it from one directory to another--no programming required.