Computer monitors

Discussion in 'Digital Photography' started by m Ransley, Dec 11, 2005.

  1. m Ransley

    Ray Fischer Guest

    He's not right. It is most certainly possible to shut off an electron
    beam mid pixel because there are no such things as pixels for the
    scanning electron beam. The intensity of the electron beam is a
    purely analog function and can be changed without regard for any
    "pixels" that may exist in the source.
     
    Ray Fischer, Dec 13, 2005
    #41
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  2. m Ransley

    Ray Fischer Guest

    Nope. You're assuming a pixel a maximum resolution but CRTs can
    handle much lower resolutions as well.
     
    Ray Fischer, Dec 13, 2005
    #42
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  3. m Ransley

    Ray Fischer Guest

    The mask on the screen has NOTHING to do with the electron beam or
    with pixels. Bandwidth does not create pixels and a CRT displying
    640x480 can most certainly control the beam mid-pixel, and the beam
    width also has nothing to do with pixels.
    Define "full res".
    An LCD has actual pixels on its screen. A CRT does not.
     
    Ray Fischer, Dec 13, 2005
    #43
  4. m Ransley

    Ray Fischer Guest

    My bet is that you're full of shit as there were no graphics boards
    40 years ago.
    Why not?
    CRTs don't have pixels. That's how you can use the very same CRT for
    a vector display.
     
    Ray Fischer, Dec 13, 2005
    #44
  5. m Ransley

    Scott W Guest

    But the feed is from a graphics board, which does have pixels. If you
    turned the beam off
    half way through one of these it would be two pixels.

    At best the analog nature of the CRT blurs the pixels that are being
    feed it, it will not add any detail that is not on the graphics board.

    Scott
     
    Scott W, Dec 13, 2005
    #45
  6. Ray Fischer wrote:
    []
    What you say is true of monochrome CRTs, but colour CRTs do have pixels in
    the form of triplets or lines or whatever. This will limit the resolution
    you can achieve.

    David
     
    David J Taylor, Dec 13, 2005
    #46
  7. m Ransley

    Leonard Guest

    Hm. I was looking at the 22" Viewsonic and the spec states it has a
    visible diagonal of 20" and a dot pitch of 0.24mm
    That implies (to me) that it has on the order of 1700 dots per
    horizontal line, yet they quote a max resolution of 2048x1536 ?

    - Len
     
    Leonard, Dec 13, 2005
    #47
  8. Making the "specification" meaningless! At least, in terms of the actual
    system resolution you can achieve - for a white beam the zero MTF would be
    at 850 cycles per picture width. You might still prefer the result of
    viewing a 3MP image at the native 2048 x 1536 rather than resampling to,
    say, 1600 x 1200, and running the monitor at a lower resolution. Probably
    different people would prefer different settings.

    David
     
    David J Taylor, Dec 13, 2005
    #48
  9. The max resolution number is probably derived purely from the analog
    bandwidth, combined with horizontal and vertical sync limitations.
    The specs are specifically written to be misleading. If you are
    lucky, each of the numbers will be correct in some sense, but never
    count on it.
     
    =?iso-8859-1?q?M=E5ns_Rullg=E5rd?=, Dec 13, 2005
    #49
  10. m Ransley

    Wayne Guest

    So this must be a CRT monitor instead of a LCD monitor.
    Dot pitch is spacing of the CRT phosphorus dots, normally measured
    diagonally. Phosphorus dots do not align with screen pixels.
    CRT dot pitch is spacing of the phosphorus dots, and is NOT actually
    related to the screen dimensions in pixels. There is only one dot
    pitch, but many possible screen size dimensions (pixels). There is not
    a match of phosphorus dots and screen pixels (yet it works very well).

    The video screen dimensions (like 1600x1200 pixel screen size)
    determines image resolution, however the largest possible screens (like
    2048x1536) probably does outrun the phosphorus dots a little (your 1700
    number). This effect is not bad at all, the important factor is that
    the dot pitch be reasonably high to look good. The specs are just
    telling you that the Maximum screen size it will handle is 2048x1536
    pixels. This is not related to dot pitch.

    On LCD monitors, there is a match with screen pixels, in that only the
    one native resolution will look very good. But on a CRT, such match is
    not important, nor specified, because all screen sizes will look pretty
    good.
     
    Wayne, Dec 13, 2005
    #50
  11. m Ransley

    miso Guest

    The high res shadow mask tubes use a funny phosphor pattern which I
    don't recall off the top of my head. However, you can tell the tubes
    that use this pattern because the horizontal and vertical dot pitch are
    not equal. See
    http://www.eizo.com/support/discontinued/crt/f930.asp
    Hitachi made the tubes. My Nokia has something similar.

    While I understand your dot density comment, I don't think it is
    achieved at even 1600x1200. For 21 inches diagonal, it would be about
    17 inches wide. FOr 3200 pixels, that would be a pitch of .0053 per
    inch. WIth 25.4mm/inch, I get a .135mm pitch
     
    miso, Dec 13, 2005
    #51
  12. m Ransley

    Ray Fischer Guest

    Which has nothing at all to do with pixels. There are color vector
    displays just as there are monochrome displays. There are NO vector
    LCD displays.
     
    Ray Fischer, Dec 13, 2005
    #52
  13. When the pixel size gets close to the dot pitch, you get aliasing
    effects like moire. The highest "supported" resolutions rarely look
    particularly good.
     
    =?iso-8859-1?q?M=E5ns_Rullg=E5rd?=, Dec 13, 2005
    #53
  14. It sets a lower limit for the size of a pixel.
     
    =?iso-8859-1?q?M=E5ns_Rullg=E5rd?=, Dec 14, 2005
    #54
  15. m Ransley

    Leo Guest

    No, I'm an electronics technologist - you are an uneducated asshole and troll.

    I don't feed trolls - bye!
     
    Leo, Dec 14, 2005
    #55
  16. m Ransley

    Leo Guest

    Nope - you're thinking of synced scan lines - I'm talking pixels!

    Tell me how many tri-phosphor dots are on a line of a TV and tell me how the PC
    can sync to them?

    The place the beam turns on and off has NOTHING to do with where the phosphors
    are placed! It can happen anywhere! The shadow mask is what makes sure the
    proper beam falls on the proper color, but it has nothing to do with sync!

    Lines and frames are synced, the video signal isn't tied to phosphor dots!
     
    Leo, Dec 14, 2005
    #56
  17. m Ransley

    Leo Guest

    Which proves what I'm saying... the phosphor area of the tube, when viewed thru
    the shadow mask, looks like a continuous area. The only breaks in the area are
    the lines of the mask.

    The beam caused by the PC signal turns on or off any phosphor it hits,
    regardless of whether or not it is contained by a single "phosphor patch" or is
    only part of it.

    Bandwidth of the monitor doesn't really apply, it's the turn on or turn off time
    of the beam that matters, and the "luck of the draw" as to where on the patch
    this occurs.

    As much as any salesman tries to tell you, CRT displays are NOT DIGITAL they are
    ANALOG!

    LCDs on the other hand are digital and the "pixel patch's" ARE synced to the PC
    graphic board, that's why you have to run an LCD at max res, or you get "off
    patch" distortion.
     
    Leo, Dec 14, 2005
    #57
  18. m Ransley

    Leo Guest

    This got cut somehow from my last post...
    Like I said, I'm talking pixels, not scan line sync.
    I'm a technician - yes! Including those old 1968 Zeniths!
    Now they don't have pixels - they are continuous phosphor...
    If the beam only illuminates a small part of the phosphor field, then the
    resolution is HIGHER not smaller!

    You'd never know... but you would on an LCD!
    I can back up what I say, do you need drawings?
     
    Leo, Dec 14, 2005
    #58
  19. m Ransley

    rafe b Guest


    Umm, bandwidth of the monitor is exactly that: a measure of how
    quickly the monitor responds to input changes. Ie. a measure of
    its how quickly it can turn on or turn off its beam.


    rafe b
    www.terrapinphoto.com
     
    rafe b, Dec 14, 2005
    #59
  20. m Ransley

    Fred Guest

    The beam shuts off at the end of the commanded pixel by the PC, but this can be
    in the middle of a phospher dot on the CRT screen... in fact, it being at the
    edge would be almost impossible! If it lined up for 1 resolution, say 1280, it
    would NEVER line up for any other! Plus there's the fact the magnetic deflection
    of the beam doesn't have a linear progression! Get a clue! This group is full
    of hat-talkers!
     
    Fred, Dec 14, 2005
    #60
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