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Seeing screendoor

Discussion in 'Projectors, Screens & Video Processors' started by Kahless725, Nov 4, 2004.

  1. Kahless725

    Kahless725
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    Hi, I am considering the Panasonic ae700 and Sanyo Z3. I will be 2.4m away and think I have worked out correctly that I will get from 40 inch to 80 screen from a panasonic and from 63 inch to 80 inch screen from the sanyo. From peoples reccomendations you need to be 2x away from the size of the screen is this diagonal as I have worked out or is it another measurement.

    Either way will only the panasonic give me a screen size that stops me seeing screen door i.e 50inch (assuming the 2 x away rule is the diagonal)

    Or will I be ok with about 68 inches on the Sanyo (as I would like)

    VB on the Panasonic has really put be off this projector and knowing my luck if I got one I would see it all the time.

    Any comments would be helpfull.


    Regards
    Robert.
     
  2. KraGorn

    KraGorn
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    Seems a bit far to me, in my experience a Z2 (same resolution as those you're looking at) viewed from 1.5xwidth distance I barely saw any screen-door on a 92" diagonal screen ... though I have to say screen-door never bothers me even on those rare occasions I notice it.
     
  3. jamesgrahamuk

    jamesgrahamuk
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    According to projectorcentral (I think) you should sit at least 1.5 to 2 times the width of the screen in order to view a properly 'resolved' image which appears smooth and artefact free to the eye. So, a 6ft wide screen should find you sitting at the least 9ft away and ideally around 12ft. I suppose that this is largely subjective...

    I have an AE700, a 6ft wide fixed screen and sit at about 13-14ft. I can see neither screendoor effect nor VB. The projector is up to 10 hours at the moment so I suppose that these are relatively early days yet.

    Even standing at a few feet from the screen I can see no screendoor effect.

    As for the AE700, I had posted these first impressions in other threads:

    "I put it through about four hours of various discs ranging from the opening planet alignment and then Blue Danube sequences of 2001 through the helicopter attack of Apocalypse Now and the crop duster scene in North by Northwest (to name but a few). I have deliberately avoided the usual Pixar demo material for now. I have to admit that I am hugely impressed. I have yet to detect any VB at all - I had expected to see it in the pale blue expanses of sky in North by Northwest - but I will keep a close eye over the next few days...

    ...I also sneaked home this lunchtime to show it off to one of my colleagues (that's the projector - dirty minded folk!) and ran through the flying wing fight from Raiders of the Lost Ark, one of the gladiatorial battles of Gladiator and (just to show off) a bit of Monsters, Inc. It was the battle of Hoth from The Empire Strikes Back which got the most oohs and ahhs though."

    Last night it was the turn of Ocean's 11, not the best of DVD transfers which the PJ managed to reproduce with wonderful sharpness. I was further surprised that it handled this films rather tricky colour scheme brilliantly - without becoming too garish (as my Tosh RPTV did with this film). Then I watched the Coen Brother's The Man Who Wasn't There; a good test of how this projector renders black and white footage - again I was very impressed by the sharpness and contrast of the image. This film features large swathes of almost blank, untextured mid-tones in many of it's compositions. This is where I had expected to encounter the dreaded VB. I didn't.
     
  4. Kahless725

    Kahless725
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    Well the main advantage to me with the panasonic would be its screen smoothing technology, this would allow me a larger picture before screendoor but I am wondering if either would give screendoor as they are high res.

    I am wondering if VB is an optical thing with the panny and therefore only at certain sweet spot distances?
     
  5. gwc

    gwc
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    Hi James

    :offtopic:

    Do you have your PJ ceiling mounted? If so, how far from the screen is it and how long is the mounting pole?


    Cheers

    gwc
     
  6. Aquila

    Aquila
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    James, what picture mode do you use? A predefined one (eg CINEMA1) or did you create your own profile?
     
  7. KraGorn

    KraGorn
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    VB is a flaw in the LCS panels' ability to generate certain colours, hence the banding instead of a continuous tone .. the ability to see it isn't a function of viewing distance.

    The 'screen smoothing' technology is a two-edged sword, while it helps reduce screen-door is also 'softens' the image, I found that somewhat disconcerting on my AE300 and was always reaching for the focus control.
     
  8. jamesgrahamuk

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    To answer most of you:

    The projector is installed on a shelf on the back wall (directly above my head) about 14ft from the screen - horizontally central with the screen but with a couple of degrees of lens shift on the vertical axis.

    I currently have it in CINEMA1 picture mode and the low lamp setting - pretty much how it came out of the box. ND, Dynamic Iris - blad-de-blah - are all ON too. Strangely, I haven't been moved to tweak it yet (and I usually have things in bits withing hours!).

    It is being fed a PAL interlaced signal from a Pioneer 757Ai over 5m component leads.

    I know that this is probably p***ing some people off - that some may think I'm half blind (or stupid) but I genuinely have not seen any VB!

    If it helps I'll post some pictures of my setup soon.

    KraGorn, perhaps Kahless725 has a point. Is it not possible that at a certain distance VB may become visually resolved? What is plainly seen as tonal variation close up becomes perceived as even (or at least more even) fields of tone/colour at greater distance.

    Tonight I shall pull a chair closer to the screen...

    (I just got the Looney Tunes Golden Collection from HMV - I thought that I'd give our film nights a classic cartoon reel before the main feature.) :cool:
     
  9. Teresa

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    i have had my ae 700 2 days same settings as jamesgraham i cant see any VB either component fed via a liteon lvd-2001 scaled up to 1080I.... must have been a dodgy batch ? as all the people who have just got thers are all
    saying no VB
     
  10. KraGorn

    KraGorn
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    VB isn't constant across an entire range necessarily, I recall when Z2s first came out several people complained about very bad banding, while others like me never saw it. I'm sure all LCD models have had problems with banding to some degree or other since AFAIK it's a result of a flaw in the manufacturing process and there are very few suppliers of panels.

    Have to say I'd not considered distance being a factor. Since VB generally shows up as darker bands of tone then I'd think that they would be detected visually from some distance, the band tend to be several pixels wide rather than a single column analogus to screen-door.
     
  11. jamesgrahamuk

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    Teresa, 1080i upscaled? Very flash... :smoke:

    Perhaps it's worth taking a quick poll of the following factors?

    What screen size are you projecting?

    At what distance is your projector from the screen?

    How is your projector mounted?
    (specify degree of lens shift and keystone)

    At what distance are you seated?

    What signal are you feeding your projector - over which cables and from which source? (specify resolution - progressive/interlaced, Component/HDMI - cable lengths, DVD model or HTPC details)
     
  12. jamesgrahamuk

    jamesgrahamuk
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    Perhaps distance is also a factor in another respect?

    I'm sitting at 13/14ft with a projector throwing a 6ft image from about the same distance. So, my projected image is exponentially less bright than someone who projects the same, or similair, sized image from a much shorter distance. Is it possible that a combination of sitting further back and a greater projection distance, producing a dimmer picture, may help obscure the VB which, as KraGorn asserts, is inherent to all LCD panels?
     
  13. KraGorn

    KraGorn
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    I'm not saying its' inherent in all panels, I don't know what what causes it to know. However given the widespread nature of this problem it seems that something in either the technology itself or the manufacturing process makes it quite a common flaw.
     
  14. Teresa

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    Hi there

    I havent got mine setup properly as yet, as i only wanted to test out my PJ in the bedroom quickly, even sat 4 feet away could see no VB or pixles for that matter.... im not sure about about scan modes and how they differ, but my liteon LVD-2001, has the p-scan button on the remote, switches between 480i, 480p, 480 i Pal, 480p Pal, 720p and finally 1080i.

    so i am unsure about which to use and the differences between 480p and 1080I but i will experiment perhaps someone can enlighten me?......but will have it set up as below

    LVD-2001>component out
    1.5 M profigold>
    Denon 3805>
    5m profigold via component >
    AE-700 dyn iris on standard settings normal viewing mode
    from 13-14 feet onto a 90 width DRH slimline
     
  15. Gary Lightfoot

    Gary Lightfoot
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    Those numbers refer to resolutions - 480 is the vertical height of NTSC (American) tv, 576 is PAL (UK). The 'i' and 'p' refer to progressive or interlaced signal, which is how the image is sent from the player to the display. Progressive has less visible horizontal lines so in theory is better.

    720 and 1080 are two resolutions of Hi Definition - 1920 x 1080 and 1280 x 720. Many projectors will display them, but some will have to scale them to fit if the pj isn't natively that res (no native 1080 projectors just yet).

    Depending on how good either the pj or the players scaling abilities are, you should try playing the same scene (or better still, a test disk), and see which resolution (i or p) looks better on the pj.

    HTH

    Gary.
     
  16. Kahless725

    Kahless725
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    What I meant was that if VB is an artifact from the way LCD outputs then this artifact may be more apparent with certain sweet spot distances, it is an optical system afterall.

    I think I am heading in the direction of the Z3 for these main reasons:-
    1. review that states it has less VB than the Panasonic.
    2. The fact that in low lamp mode it is 3dB quieter than the Panasonic.
    3. The fact that you get a generous 3 year warranty whereas you get a measly 1 year one with the Panasonic.
    4. From the distance I am going to use it then screendoor sounds like a non issue so I do not need the smoothvision of the Panasonic and would prefere the frequently described as more sharp Z3.
    5. I can get a black Z3 (the new silver)
    6. The Z3 is a little cheaper.
    7. The lens shift of the Z3 will mean I definately can have the picture with zero keystone correction.

    The main plus point and one that nearly swung it for the Panasonic was the smoothvision but :-
    1. The image has been reported as less sharp because of it.
    2. It is not an issue with this res projector and my distances.


    I will of cause test before I buy but I am 90% sure what I will go for.


    Comments?

    Regards
    Robert.
     
  17. Kahless725

    Kahless725
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    From number 3 above I was sure the Z3 had a three year warranty but now I am reading 2? ahh well still twice as long. (3 with Barclaycard)
     
  18. zAndy1

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