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Sony HS1: Screendoor and defocusing

Discussion in 'Projectors, Screens & Video Processors' started by MainMan, Jan 5, 2003.

  1. MainMan

    MainMan
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    I'm one of those who are sometimes irritated by the screendoor issue on my PJ. A common advice for alleviating this is to defocus the picture slightly. However, on my Sony Cineza VPL HS1 at least, when I defocus, the effect is skewed to one side. That is, I can't get the picture to be defocused by the same amount from left to right. Anybody have any thoughts on this?
     
  2. Gary Lightfoot

    Gary Lightfoot
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    Do you have a white screen?

    Sometimes going from a white screen to a grey screen can give the impression of reduced screendoor - the grid lines are less noticeable on a grey screen when compared with a white screen.

    Also, sometimes using a filter on the lens has a similar effect.

    I can dig out some links for you if you like if you think trying either of these is worth the bother.

    Not sure why the defocussing isn't uniform, unless the lens thread/fockusing mecahnism isn't square for some reason.

    Gary.
     
  3. MainMan

    MainMan
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    Thanks Gary, so you're saying that there might be something wrong with my particular HS1 unit regarding the focusing? Can other HS1 Cineza owners confirm whether the changing of focus occurs uniformly across the picture? (Mine is skewed quite a bit).

    The grey screen idea makes sense - one just have to contemplate what this does to the rest of the picture... I'll keep it in mind if I'm going to upgrade to a new screen.

    I already am using a filter, the one supplied by Sony in the box. This is not for alleviating screendoor, however.
     
  4. Gary Lightfoot

    Gary Lightfoot
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    Hi mainman,

    I wouldn't like to say if there wasn't anything wrong with the focusing mecahanism, it might just be a quirk or maybe the pj is slightly twisted to one side? That might explain why it doesn't have uniform focus. Try rotating the pj one way or the other slightly, and see if the focusing becomes more consistent across the entire screen.

    This isn't as unlikely as it seems - my pj seemed perfectly square, but I noticed the image dropped down slightly at the bottom l/h side. Moving the pj 2 inches sideways squared the image up, so it might be worth looking at that perhaps. In my case the pj was pointed very slightly to the left IIRC, which is what caused the image to be larger and appear to drop down.

    Grey screens will reduce peak white, but the eye doesn't notice this unless you have a white screen next to it to compare. The lightest part of the screen will look white due to the way the brain works in translating what it sees. The eye is more sensative to black level than peak white.

    Grey screens help reduce the effect ambient light may have on the projected image, and also increase percieved contrast. They also improve black level, which is why it is a screen that is normaly only used with digital pjs.

    Go here for an interesting read on the matter.

    As for a grey screen reducing screendoor - it seems to only be percieved when compared with a white screen. The darker grid lines of the screendoor are more of a contrast against a white screen than a grey screen, so seem more prominent. When they beta tested the Stewart Grayhawk screen, the majority of the testers reported a reduction in percieved screendoor. Conversely, someone without a white screen as a reference (in a demo room seeing their first grey screen) thought it increased screendoor, so your milage may vary.

    The filter that came with your pj is for correcting the colours to make them more accurate. Some use an FLD filter to reduce the green push some LCDs have, and some use a CCR30 to improve reds (IIRC).

    I have read that a lens filter has had a similar effect on reducing screendoor, but if you haven't noticed it with the filter you have, then the chances are you won't with another filter.

    HTH

    Gary.
     

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