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convergence and geometry, redux

Discussion in 'Projectors, Screens & Video Processors' started by Matinee, Feb 5, 2003.

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  1. Matinee

    Matinee
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    I'm still having to adjust convergence more than should be necessary. Trying to get good convergence at 1440x810x75Hz whilst not pushing settings - I realise the higher resolution will make convergence higher.

    When set to midpoint the convergence on the left hand side of the screen, particularly upper left is drastically out, less so on the right hand side. Red is much worse than blue. When doing the central convergence point (raster shift) it is not even always possible to get the red on green on both sides of the zone precisely.

    One point: I have not touched any mechanical adjustments, aside from a small modification to blue focus at one point that was subsequently returned to the original focus position.

    I'm a little confused by the raster shift option. There is the central raster shift zone in convergence, the raster shift option in geometry and the raster shift option in service. I can see the raster by turning up brightness and down contrast and when everything is at midpoint it's fine. To fit the 16:9 screen requires a small amount of vertical raster adjustment (as there seems to be no 'V-Phase' option). I also have to set v size to 20 something and h size to 70 or so.

    Once the h phase/v size/hsize has been modified to fit the screen, the active raster area is still well within the phosphor, but the considerable glow behind it is not. I presume this is correct, as I cannot see how it is possible to fit the screen otherwise. It is only the active area that causes issues, is it not?

    I note that the safe zone for convergence is listed elswhere as 'around 30-70', with the note that geometry can be pushed much harder - I cant find any details of how hard is safe however.
    The most I've had to go is about 30 for bottem bow and 70 for keystone.


    From experimenting it also seems that some settings affect others (keystone seems to be a combination of centreline adjust and another setting for instance), and that geometry can make convergence harder. It's also apparent that frequently in convergence, one zone may have large effects on the convergence of others whilst other zones will barely change in convergence regardless of how high the settings are.

    Finally I note in another post Roland recommends getting the convergence geometry correct on a 15Khz setting, that will then serve as a basis for stable convergence at other resolutions.

    So, questions:

    What is the situation with raster usage?
    If 30-70 is the limit for convergence, what's safe for geometry ?
    Are there any notable geometry settings that have a severe impact on convergence?
    What's the situation with the 15Khz setting?
    and
    is there likely to be anything else going wrong?

    I'm happy to tweak until the system is right, but dont want to do any damage whilst doing so.

    PK
     
  2. Matinee

    Matinee
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    Additional thought : I'm running multiple resolutions at 72Hz... this is not going to work unless i use input 95 for one of them.

    Block delete time and more tweaking tonight I think.

    PK
     
  3. Roland @ B4

    Roland @ B4
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    I doubt very much that you will get good stable convergence at that resoloution. In fact it's beyond what a 700 series projector can do anyhow.
    Drop it down to 800x600@75hz. and it will become far more stable.

    I don't recall advising using the 15khz as a base but you never know. I would always chose a mid range setting between the frequencies that you are most likely to do. that way if you are going to keep changing resolutions then the projectr should come with a common setting.
     
  4. Matinee

    Matinee
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    Thanks for the response Roland, but the projector is a BG1208, not a 7xx series.

    PK
     
  5. Roland @ B4

    Roland @ B4
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    OOPs:blush:

    One of mine too.
    Peter I have at long last manage to send a long email to you.
     
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