Re: The case for lower case

Randall Hyde wrote:

>
> As for monitor foreground and background colors, the easiest to read page is
> one that comes closest to matching the 18% gray scale that are eyes are
> accustomed to seeing in nature. That is, 72% white and 18% black. Easily
> achievable by putting black letters on a white background. Difficult to
> achieve (in a readable form) by putting white letters on a black background
> (too much contrast). This, in fact, was the reason for green screen monitors
> in the first place -- it reduced the contrast.

White phosphor (for instance P4) isn't commonly used for mono CRTs,
although HP and Xerox used to make them. Its whiteness & blackness was
always a little suspect (most white phosphors look grey when on; and
they just look less grey when off), so the contrast was noticeably low.


And with low persistence it demands higher refresh rates. Perceptible
flicker was common with these screens, especially under neon light.
Very poor in reverse video (i.e. black on white) as that demands very
high power output from the electron gun, good power regulation and high
scan frequencies -- which means expensive. Your average 20 year old
black & white television displays these symptoms in spades. Displaying
more than 20 lines of 40 characters in reverse video on the average
modern CRT based TV is still more than most can handle.

Green phosphor (P1) was used because of its relatively high light
output, and its persistence that reduced flicker with low scan speeds
(and hence the manufacturer could get away with cheaper electronics);
reduced contrast would be a secondary effect. Some of these screens
were amazingly sharp, as good as modern LCDs.

In the end, though, all down to price.

--
Regards
Alex McDonald

.

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