Digital Convergence

Discussion in 'Archived Threads 2001-2004' started by Rick_E, Jul 1, 2002.

  1. Rick_E

    Rick_E Agent

    Joined:
    Jul 1, 2002
    Messages:
    32
    Likes Received:
    0
    Hello All,

    I've looking at the HTF forum for a while, and have really enjoyed it. All of you are have great insights into films, dvd, hardware, etc.

    I'm getting ready to purchase my first HDTV...I already have a nice reciever, dvd player, etc. My question is...what is "Digital Convergence", and is it important for a HDTV to have it. For space and budgetary considerations, I'm looking at the Samsung TXM-3096WHF 30" direct view widescreen. Any comments on this unit in general? I know that it DOES NOT have digital convergence, hence the question.

    Thanks for the help...and for the educational pleasure of wasting hours reading all your posts!
     
  2. Steve Schaffer

    Steve Schaffer Producer

    Joined:
    Apr 15, 1999
    Messages:
    3,756
    Likes Received:
    1
    Rick,
    Convergence, digital or otherwise is an issue with crt based rear projection tvs-the most common type of rptv. These use 3 separate picture tubes--red, green, and blue to project the image onto a mirror which bounces it onto the backside of the screen. The 3 separate images must all hit the screen in exactly the same place in order not to have color fringes around the edges of images on the screen.



    The set you're considering is not an rptv, so convergence isn't an issue, which is why it doesn't have "digital convergence."
     
  3. Rick_E

    Rick_E Agent

    Joined:
    Jul 1, 2002
    Messages:
    32
    Likes Received:
    0
    Steve,

    Thank you...that actually makes a lot of sense. I appreciate it.
     
  4. Allan Jayne

    Allan Jayne Cinematographer

    Joined:
    Nov 1, 1998
    Messages:
    2,404
    Likes Received:
    0
    Digital convergence uses a microprocessor to keep reasonably precise control over the electron beams and fine tune their travel paths to remain juxtaposed. The screen is typically divided into fifty (49; 7x7) to 100 (10x10) zones. The zones do need manual setup.
    As the electron beams enter another zone, a different set of steering currents is applied to the coils around each picture tube neck. The more zones there are, the less chance a beam has to get out of line.
    Whereas analog convergence relies on ring magnets or physical positioning of yokes and coils on the picture tube(s)' neck(s), and settings of potentiometers (pots) and usually there are no more than nine (3x3) zones, also requiring manual setup at the factory and/or in your home.
    It has been said many years ago, before they invented digital convergence, that one half of one percent convergence error is acceptable near the screen corners, but that equals two to three scan line thicknesses.
    Digital convergence is more precise but doing the fine tuning (manually every year or so) to keep it precise is more work on your part or on the part of a serviceman or ISF technician.
    Most people find that screens under 36 inches don't need digital convergence, but I have seen sets that size and smaller playing in stores with horrible misconvergence. You should actually see the exact set you will be buying played in the store for a few minutes before you pay for it and take it home, to be sure convergence is OK.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     

Share This Page