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Focus not as clear on botton of Screen with Runco 940/Barco 708

Discussion in 'Projectors, Screens & Video Processors' started by ScottMcDonald, Oct 4, 2005.

  1. ScottMcDonald

    ScottMcDonald
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    Am I just seeing the weakness of my Runco 940/Barco 708 and my HTPC. My convergence appears to be dead-on. Picture looks great except the very bottom of my screen appears to be not quite so focused as the rest of the picture. When my Windows XP screen pops up and I look at the menu bar with the current time in the corner....that bottom part of the screen just doesn't want to focus as well. If I move the menu bar to the top of my screen it appears to be in better focus than the bottom.

    Any Ideas? I'm not really worried about it since the movies look fantastic. Just looking to do my final tweaking....(but is there really any final tweaking with us???)

    Thanks,
    Scott

    Oh...the screen is homemade...JoAnn's blackout fabric....96" across by 54" vertical....
     
  2. Gary Lightfoot

    Gary Lightfoot
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    Could it be possibly that the pj is angled slightly more than is recommended, so that the bottom of the image is outside of the focal range so looks a little blurry (whereas the rest is within the focal range)?

    Gary.
     
  3. cosaw

    cosaw
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    Yes it seems there is little that it could be appart from a focal problem like Gary suggested.

    One thing worth checking before you delve deeper. Check your lenses - i got a large smear of grease on the bottom of one of my lenses and thought I had a mechanical focus problem but found that the grease was slightly diffusing the image on one of the tubes seeming to make the pic a little soft/blurred.

    After that make sure you've done everything in full and in the right order during setup. Best place to start is with all data blocks erased from the memory and everything set to midpositions. Its the only real way to work out where your errors are creeping in in my oppinion. This may not be desiralbe if you've paid and had a proffesional setup done and may be worth contacting the installer if they are reputable and know what they're doing.

    Double check everything: Firstly and of major importance make sure your screen is square (not bowed in any direction like my frame and canvas screen can be and needs to be tweaked into line) and face on to to your pj so that the pj is at 90^ to the screen in both the horizontal and vertical plane. A spirit level front to back and left to right on the top of your pj will help determine this if you have it ceiling mounted. So pj level with floor and screen perpendicular to the floor. If you're screen is angled up or down then the key is to get the pj at 90^ (in this case a spirit level front to back is of no use but left to right is still worthwhile).

    One thing to note some projectors have spacer washers behind the lenses where they mount to the crt housing. If your screen size is over or under a particular size these spacer swashers need to be in different places - you can only find this from the specific projector manual or someone who knows. These washers help bias the lens angles so they are suitable for screens under (so many meters) or over (so many meters). Its worth checking if you've got the right washers in the right places before going through any of the instalation setup.

    Then go through the instalation setup in the menu doing raster centering and cross hair alignment as required and lens flapping if your pj has it. Getting all the above right should cure any lens focussing problems. Then go onto geometry and convergence after getting all that right.

    Its always worth going back to basics to try and sort these sorta problems out. Rule out the obvious stuff then try something else if it doesn't fix the situation.

    Hope this helps.

    Simon
     
  4. kalW

    kalW
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    If it's a gradual thing (ie: the focus gradually gets worse as you go from top to bottom) then it's most likely that the projector's not 100% square to the screen.

    This PJ does have scheimphlug (lens flapping) adjustments on the tubes. That could be off as well, or simply not set up correctly. If you're not familiar with this, see the install manual available here: http://www.curtpalme.com/Barco701.htm

    Kal
     
  5. ScottMcDonald

    ScottMcDonald
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    Well, I want to thank you for your replies. I did set up the projector myself. And....so I probably not quite 100% square. I would guess that the best way to check for this would be using a laser square and range device to determine which axis is off.

    Thanks again for your help!!!

    Scott
     
  6. kalW

    kalW
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    Did you do any scheimpflug adjustments at all on the tubes after installation?

    If not, I'd just start there. Turn on only the green gun, throw up a test pattern on screen and follow the scheimpflug adjustments in the manual link I posted above. If your mech. install is too far off then you won't be able to compensate with scheimpflug and you'll have to remount the projector. The idea with scheimpflug is to get the entire screen *even*. Evenly in focus (or out) of focus first, then use the two focus knobs on the tube to dial in the focus (center and edge focus). Then do the same for the other tubes.

    Kal
     

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