Keystone question

Discussion in 'Archived Threads 2001-2004' started by Greg Miles, Feb 2, 2002.

  1. Greg Miles

    Greg Miles Extra

    Joined:
    Jan 27, 2002
    Messages:
    15
    Likes Received:
    0
    Gang,

    If my projector has a fixed 16 degree keystone setting is there a specific height from ceiling or screen height that I need to observe when setting it up for a given distance from the screen? A formula ?
     
  2. Greg Miles

    Greg Miles Extra

    Joined:
    Jan 27, 2002
    Messages:
    15
    Likes Received:
    0
    Anyone?
     
  3. Allan Jayne

    Allan Jayne Cinematographer

    Joined:
    Nov 1, 1998
    Messages:
    2,404
    Likes Received:
    0
    Most people don't worry about a slight keystone error. The projector with just one fixed keystone compensation adjustment gives a reasonable picture with the projector on the ceiling over a range of reasonable distances giving a range of reasonable picture sizes.
    If there is just one fixed keystone setting, then there is exactly one screen distance at which the projector is level with the top of the screen and the picture is exactly rectangular. Closer to the screen the projector has to be below the screen top, further from the screen the projector has to be above the screen top to keep the picture rectangular.
    If the one and only keystone compensation angle is bigger, the projector to screen distance magic number where the projector is level with the screen top is smaller for a perfect rectangular picture.
    (If the keystone adjustment is zero, the picture is precisely rectangular only when the projector is level with the exact screen center, or in other words the distance when the projector should be level with the screen top is infinitely far away.)
    There are formulas but I don;t know any of them.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     

Share This Page