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Screen ratio question

Discussion in 'Projectors, Screens & Video Processors' started by DavidPeat, Nov 17, 2003.

  1. DavidPeat

    DavidPeat
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    Hi

    I have a PTAE-100 and a 7ft 16:9 Luma Draper screen, mounted behind the curtain pelmet.
    Originally, I had the projector on a coffee table with the keystone set arounf 8 or 9 and this worked well and the image perfectly fitted and filled the 16:9 screen.

    I have now ceiling mounted the projector at about the same distance - maybe a foot further back and the keystone is now set at 6 or 7 to get vertical edges. The problem is that when the image fills the screen horizontally, it now overlaps the top and bottom by a couple of inches!

    It doesn't really bother too much during viewing but you know what perfectionists us HC fans can be :D

    Anyone have any ideas? The only thing I can do to make it fit properly is to pull the bottom of screen outwards by a few inches , thus narrowing the angle of incidence very slightly.

    Cheers
    David
     
  2. buns

    buns
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    you arent somehow squicshing the image horizontally? I can do this with my pc for example

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  3. bibooo

    bibooo
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    I may be missing something here, but can't you just zoom the image in slightly thus reducing the image size?
     
  4. buns

    buns
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    but then the image wouldnt fit horizontally and there would be empty bars at the sides

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  5. Sandman

    Sandman
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    I have experienced the same problem with my AE100. I had my projector ceiling mounted and when it was switched on I painted my screen onto the wall so the image exactly fitted the painted screen.
    At the weekend I swapped my argos speaker brackets mount with a much better ceiling mount. Now the projector sits lower down and is about 6 inches further away from the screen. Anyway when I zoom the picture to fill it vertically the picture overlaps the screen edges by a couple of inches. The projector keystone was set to zeor and is now set to 2. It is as if by using the keystone you change the aspect ratio of the picture.
    Need less to say I got the paint out right away and amended my screen.
     
  6. SanPedro

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    The difference (i think) is because the keystone is working in the opposite direction and is having to shift the image more (when working from a high position) than from a lower position. Try inverting your projector and then inverting the image. If the PJ is now the same distance from your ceiling as it was from the floor on the coffee table then the keystone should be the same.

    When the PJ is on a coffe table, as you describe, the normal projection of the image is slightly upwards, rather than dead ahead. So when you mount the PJ on the ceiling you need to put more keystone in as it is having to push the image down further.

    So to get around this you mount the PJ upside down. This way the keystone will be less.

    Make sense?

    Chris
     
  7. DavidPeat

    DavidPeat
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    Thanks for all the replies.

    To Chris, the projector is upside down on the ceiling i.e. when I look up at the projector, I am looking at the buttons on top. I mounted it using the top assembly off an old camera tripod I had.

    So, roughly speaking (considering the almost identical keystone numbers used) the geometry of the setup is almost the same, except inverted. The projector is roughly the same distance above the top of the screen now as it was below the bottom of the screen when it was on a table.

    Cheers
    David
     
  8. Sandman

    Sandman
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    David, I dont want to worry you but I wouldnt advise using the tripod connector to hang you panny. apparently this is only glues onto the casing and might not be very safe.
     
  9. bibooo

    bibooo
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    Aaaaah, it all becomes clear. I knew I should have read your post properly. Perhaps a bigger screen is in order, or you could paint the curtain pelmet white, and hey presto bigger screen. :D
     
  10. DavidPeat

    DavidPeat
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    Sandman, I had a good look at the tripod mount and didn't see/feel anything that gave me concern but your point is noted - I'll try and not swing from it (the chandelier in the bedroom is for that :laugh: .

    Hey, even if it did give, it would still be dangling from the ceiling from the VGA cable ;)
     
  11. SanPedro

    SanPedro
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    David

    Just a quick question ... have you always had a screen with the Panasonic? I have the exact same video set up, except I currently have a blackout blind doing the screen honours at the moment. I was wondering about getting a screen and was interested in knowing what improvements there are. Did you go for white or one of the grey screens that Draper do?

    Regards

    Chris
     
  12. DavidPeat

    DavidPeat
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    Hi Chris

    Yes - I've always had a screen. It is a white Draper Luma 82" I think - not quite 7' diagonal.

    I cannot comment on the differences between it and a blackout. I don't know if any other forum members have actually done a side by side test? Having lurked here for a while, I would be very surprised if someone here hasn't :)

    One thing I have noticed over the last year, is that there are slight wrinkles at the lower corners of the screen. These are barely noticeable, and only when there is a horizontal pan across light colour such as sky. Also I have noticed (on similar scenes) a very slight, barely perceptable vertical banding but I am not sure if this is due to LCD panels, the source or the screen. There is certainly no sign of this on inspection of the screen itself but there is a certain 'graininess' to the screen surface so maybe it is this?
     

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