> It was cheaper to manufacture a display that produced bright text on a black background - fewer pixels to light.
Btw, I hope that was a completely tongue in cheek remark.
Monitors don't work like photocopiers and toner. The whole inside of the CRT was coated with phosphors, and an electron beam scanned across them, changing intensity to determine the brightness of a so-called pixel. As the beam is only "drawing" one dot at a time, it doesn't really care whether your whole screen is on or off.
Which brings up yet another reason a monochrome CRT was less fatiguing than a color one showing black and white: the color CRTs required a triad of phosphors and a shadow mask screen to help the beam hit the right phosphors, cutting visual resolution to less than a third of what a monochrome would offer.
Btw, I hope that was a completely tongue in cheek remark.
Monitors don't work like photocopiers and toner. The whole inside of the CRT was coated with phosphors, and an electron beam scanned across them, changing intensity to determine the brightness of a so-called pixel. As the beam is only "drawing" one dot at a time, it doesn't really care whether your whole screen is on or off.
Which brings up yet another reason a monochrome CRT was less fatiguing than a color one showing black and white: the color CRTs required a triad of phosphors and a shadow mask screen to help the beam hit the right phosphors, cutting visual resolution to less than a third of what a monochrome would offer.