VPL-HS51A Focus Question

Discussion in 'Projectors, Screens & Video Processors' started by olivier21, Mar 10, 2006.

  1. olivier21

    olivier21
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    VPL-HS51A Focus Question

    Hello all
    My name is Olivier and I am in the process of finishing my home theater and I need some advise. I am building a home theater and purchased the Sony VPL-HS51A. I never had a projector before. The projector throw distance from the screen to the lens is 198 inches and the heights of the projector is 75 inches, projecting on a Dalite high contrast cinema contour perforated 106 inches. Right now I am using the component output via DVD player and using the AVIA calibration DVD for this test.

    The Sony VPL-HS51A is pretty good so far but I believe I have a focus problem with it or seems to be that way. Since some of you have a VPL-HS51A and are very knowledgeable about it I figure I would ask you my question.

    My question is when I adjust the focus of the projector using the test pattern from AVIA DVD I see noticeable horizontal lines across the entire screen. So when I adjust the focus and change to a less sharp image the lines disappears. So the picture is always soft. It is very difficult to watch a movie with those lines across the screen. the lines are more present in the whites. Now the only thing that I have not try is to take the projector off the mount and moving the projector placement, like a foot forward or a foot backward.

    I would extremely appreciate if you could help me before I spend endless time on the phone with Sony customer service. Thank you in advance.

    Here is the link to my AVS forum site with a picture of the focus problem. It's called "AVIA focus test 1"
    http://gallery.avsforum.com/showgallery.php?cat=500&ppuser=7535598
     
  2. kurtz

    kurtz
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    Hi Olivier,
    The speakers look well hidden - are you using a perforated screen?
    I ask because it is possible to get interference patterns with perforated screens.

    If you zoom the image in or expand it out (but keep it sharply focussed) does the pattern change?
     
  3. olivier21

    olivier21
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    Thanks Kurtz

    Yes I am using a perforated screen. I did know you could get interference patterns with
    a Perf screen. Absolutly if I zoom the lines changes shapes. At first it's very horizontal
    (see picture in link) and if I zoom the lines start to curves. Your are right.

    What can I do to avoid this ?

    Thanks again.
     
  4. kurtz

    kurtz
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    Well, you've already tried the two most common solutions - defocus or change the image size. But neither sound satisfactory. The pattern changes when you vary the image size because as you enlarge/reduce the image you vary the pixel pitch of the projected image - so the ratio of the projected pixel pattern and the fixed perforation pattern changes. Sometimes you can hit a "sweet spot" where the moire effect is reduced - but its a huge compromise.

    With LCD, particularly, the grid pattern is more pronounced, but this effect can happen on any pixel projector with a perforated screen.
    See this article from digital projection.

    Changing your screen to be non-perforated and moving your speakers would be a definite - but disruptive! - solution. Or you could try screenresearch.com. Acoustically transparent screens from Screen Research (the Clearpix range) have a very good reputation because they are not perforated but are tightly woven with a diagonal weave that should be too fine to cause any moire patterns. However, the clearpix material is only available in unity gain or less - so you need to consider the brightness with the Sony - although that may still be comparable with the gain of your current screen.
     
  5. olivier21

    olivier21
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    First of all thank you very much for your answers and resources.
    Over the week-end I tried to find the "sweet spot" by moving my entire PJ base 16 inches foward and lower it. But no luck the horizontal lines patterns were there no matter what I did. I even tried to put the PJ on the floor but it was the same.
    This is my first LCD projector and in a couple of years I would like to upgrade to LCOS so hopefully the problem will not come back. In the mean time I will defocus the picture just enough so I don't see the lines. Thanks again for the info on Screen Research.

    Olivier21
     

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