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Thread: Monochrome VGA monitors: different types of phosphor

  1. #1

    Default Monochrome VGA monitors: different types of phosphor

    I have three monochrome VGA monitors, all apparently 'white' but only one has white phosphor, as far as I can tell. The other two appear to be a composite of yellow and (possibly) blue. It's not easy to tell, except by moving one's eyes quickly while a high-contrast image is on the screen.

    The white on the composite phosphor displays is slightly greyer too. These two have shorter duration (the pure white one ghosts a lot) and are a little more flickery.

    I'm guessing that in the late 80s/90s, a monitor described as paper-white or paperwhite actually had white phosphor, whereas standard mono VGA displays may not have done. Does anyone know of any brands - preferably European as I'm in Germany - that were definitely made with white phosphor?

    Or is the yellow/blue effect a visual artefact of a fast-decay phosphor, and paperwhite displays just had longer duration? I used to own an Amstrad paperwhite VGA monitor and that was definitely truly white.

  2. #2

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    P4 is the standard short-persistence white phosphor, used by black & white TVs. But some "white" CRTs, such as in the Apple Lisa, are actually blue with green persistence:



    Many older monochrome CRTs were medium or long persistence, to reduce flicker, but with VGA, text mode is 70 Hz so flicker isn't much of an issue for most people, allowing the use of short-persistence white phosphor.

  3. #3

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    I've got this one:

    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

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  4. #4

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    Quote Originally Posted by AlexC View Post
    Or is the yellow/blue effect a visual artefact of a fast-decay phosphor, and paperwhite displays just had longer duration? I used to own an Amstrad paperwhite VGA monitor and that was definitely truly white.
    See here on "Paper-White Phosphors"... apparently they did use a blend of blue and yellow (and some pink).

  5. #5

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    Quote Originally Posted by VileR View Post
    See here on "Paper-White Phosphors"... apparently they did use a blend of blue and yellow (and some pink).
    Ah, that explains it beautifully, thanks. Though I'll have to take a microscope to my 'true' white one and see what colours it actually uses.

  6. #6

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    Quote Originally Posted by vwestlife View Post
    P4 is the standard short-persistence white phosphor, used by black & white TVs. But some "white" CRTs, such as in the Apple Lisa, are actually blue with green persistence:



    Many older monochrome CRTs were medium or long persistence, to reduce flicker, but with VGA, text mode is 70 Hz so flicker isn't much of an issue for most people, allowing the use of short-persistence white phosphor.
    I always thought the old Apple screens looked more blue-ish than later PC monitors, though I guess the camera accentuates it in that clip.

  7. #7
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    I have no knowledge of the phosphor makeup of the mono VGA monitors, but I do remember having 256 shades of gray on some of our mono VGA workstations back in the day. IIRC, they didn't last very long in the work place. I seem to remember 17" color VGA with progressive scan going for slightly under $600 in the early to mid 90's. Apologies for slightly derailing this thread.

  8. #8

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    Quote Originally Posted by Agent Orange View Post
    I have no knowledge of the phosphor makeup of the mono VGA monitors, but I do remember having 256 shades of gray on some of our mono VGA workstations back in the day.
    Standard VGA only has 64 shades of gray because a monochrome VGA monitor only uses the green pin; it doesn't combine R+G+B.

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    Quote Originally Posted by vwestlife View Post
    Standard VGA only has 64 shades of gray because a monochrome VGA monitor only uses the green pin; it doesn't combine R+G+B.
    No argument from me on that. Maybe confused 256 VGA color pallet in the mono mode?

  10. #10
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    Radius designed their monochrome monitors to do 256 shades of gray with special drivers.

    Having had an IBM 8503, I found it difficult to tell the difference between more than about 6 gray shades counting white and black.

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