Screen Door Effect...what exactly is it?

Discussion in 'Displays' started by Evan_B, Feb 4, 2006.

  1. Evan_B

    Evan_B Auditioning

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    I have been looking at the Sony KDF-E42A10. It is an LCD rear projector.

    It seems to have a tremendous picture at the store but I have heard to beware of SDE in LCD rear-projectors.

    I did notice some pixilation but what excactly is meant by SDE? I did notice small squares but that was when I got up within a few feet of the screen.

    Are the pixels the screen door effect or is SDE literally the small blocks when you put your face up to the screen?

    Can someone help clarify? And while you're at it, any thoughts on the Sony 42'' I'm looking at?
     
  2. Charlie Campisi

    Charlie Campisi Screenwriter

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    SDE is exactly that. When you get up close you can see the "breaks" between the individual pixels and it looks like you are watching through a screen door. I haven't compared it from display to display, but I suppose some could be worse than others. I think the key is to stand the appropriate distance when shopping so that it matches either your primary viewing distance at home, or the closest anyone will sit. If you can see the SDE at that distance, you should go with a smaller display, or move back. Unless it doesn't bother you. Usually, once you know it's there, it will bother you to the point of distraction, so get the right size display for your seating distance. [​IMG]
     
  3. Phil Taylor

    Phil Taylor Supporting Actor

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    You may want to look at a DLP RPTV if you are overly concerned about the SDE. Or if you have the funds take a look at the Sony SXRD line. Both formats have better fill and contrast ratios than LCDs.
     
  4. Steve Schaffer

    Steve Schaffer Producer

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    I have a 57" crt based HD RPTV that looks great from my normal viewing distance of 13 feet yet is a mess if I get within 4 feet. All the crap I see up close disappears from a normal viewing distance.

    I've been to any number of stores that have the Sony LCD sets parked right next to DLPs, and the SDE disappears at anything approaching a normal viewing distance. The nasty pixellation and motion blur on the DLP sets doesn't though.
     
  5. Wayde_R

    Wayde_R Stunt Coordinator

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    It seems when judging image quality on HD there are several things that could cause what we're calling "pixelation". "motion blur"? I believe it's either bad 2:3 pulldown or just macroblocking causing visible pixels to appear when things move fast on screen.

    I have a Sony LCD RP and I am aware of the screen door. I only see it when the screen gets bright especially bright white. Otherwise I don't notice it from a normal viewing distance.

    As far as I've seen, on any fixed pixel display you see pixels if you get close enough. Even DLP/Plasma have pixels.

    Macroblocking is interesting. HD broadcasts uncompression rate is finite. When things move fast there is more information than mpg2 can handle. The images in that post show macroblocking at work.

    One thing I notice at TV shops is the HD demo might show something move quickly and macroblock. I wonder how many would be customers blame the display technology, TV or manufacturer etc.

    I suppose it's possible some TVs with a really good video processing can limit the effects.
     
  6. Jay Mitchosky

    Jay Mitchosky Producer

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    Absolutely. While DLP and SXRD/LcOS have better fill factors then LCD (ie. more space on the panel occupied by pixels vs. gaps) at appropriate viewing distances SDE goes away. DLP and SXRD/LcOS will allow you sit closer to the screen while with most LCD you'll need to sit farther away. There are different schools of thought as to recommended viewing distances but most agree that it should deliver a minimum 30 degree field of vision. You can also consider where you like to sit at the theater. If you prefer farther back then you'll set yourself the same way at home and can also accomodate a wider variety of display techologies. Alternatively closer seating distances (with larger fields of vision) will dictate techs with higher fills. As 1080p becomes more mainstream these differences will be less distinct.

    As an aside SDE bothers some more then others. See what camp you fall into. Secondly, there is a product on the market from Cygnus that optically splits the pixel structure to reduce SDE. Might be an alternative if you've otherwise found the projector you like. Not cheap, though. About US$500 if I recall. There is also at least one LCD projector (Panasonic PT-AE900) that uses a smoothing technology to reduce pixel structure (actually eliminates it at any reasonable viewing distance). Lots of argument across the 'net as to whether it unduly softens the image as well.
     
  7. Dean L

    Dean L Stunt Coordinator

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    So would the SDE be noticable on the KDF-E42A10 from a distance of about 7 and a half feet?
     
  8. Charlie Campisi

    Charlie Campisi Screenwriter

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    Depends on how good your eyes are. [​IMG] Seriously, that's something you need to check for yourself. No one else can tell you, aside from maybe saying some models are better/worse than others. Find one on display, count off 7 feet and check it out. No other way to do it.
     

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