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Off-centre projectors...

Discussion in 'Projectors, Screens & Video Processors' started by j05ha, Nov 15, 2003.

  1. j05ha

    j05ha
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    Hi all,

    I'm new to this so go easy on me, I've searched the forums already but can't find what I'm looking for.

    Can anyone reccomend a projector cablable of being mounted off-centre? I'm aware of Sony's Side Shot(TM) technology but does anyone else offer a similar thing?

    Btw - cost is an issue so sub £1500 would be ideal and is to be used primarily for data projection.

    Any help is very much appreciated!

    Cheers,

    J.
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Immersive Virtuoso does this extremely well. Except it's about 5 times your budget.....
     
  3. j05ha

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    Thanks, but as you say it is a touch over budget! Nice piece of kit though....

    Surely this functionality is available at the lower end from someone?

    Cheers,

    j

    PS - pls excuse my spelling!
     
  4. silent lucidity

    silent lucidity
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    How about the lens shift feature on the Sanyo PLV-Z1 and the imminent PLV-Z2?
     
  5. MRW

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  6. Stereo Steve

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    How does Lens Shift differ from keystone correction? I understand that to position a PJ to the side as you can with the Sony, you need horizontal keystone correction.
     
  7. j05ha

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    From looking at all these it seems the 'lens shift' feature is basically a form of horizontal keystone.

    The NEC can be placed at 30deg to the screen although I think this would depend how far away it is. I'm not sure how this compares to the Sanyo or Sony (if you believe the sony brochure it looks as though it can placed at >45deg!!)

    Has anyone used either the Sanyo or the NEC?

    Again, many thanks for all your help!

    J.
     
  8. Warpaint

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    This might seem like a strange reply, but...
    If you are mostly displaying computer presentations why not try rotating your data by 90 degrees and sitting the projector on its side. You could then use the keystone adjustment to correct the shape.
    Note. keystone adjustment (both horizontal and vertical ) will gratly reduce the displayed resolution of the projector.
    I would always try to get directly in front of the screen and use no keystone at all if possible.
     
  9. yatesd2404

    yatesd2404
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    Hi,



    The Sharp XV-90/91E does both horizontal and vertical keystone correction and would come in around your budget (last time I looked anyway).

    Not sure what the max., off centre position allowed/capable is, but I do have the electronic user guide that covers this if you are interested.



    Cheers,

    Dave.
     
  10. buns

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    the sanyo lens shift is supoosedly unique from keystoning in that it shouldnt be introducing distortions like keystoning will

    ad
     
  11. JUS

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    I've got a Sanyo Z1. I don't have it in a fixed position. So I just plonk it down and turn it on. It's never usually dead center.

    Lenshift allows me to position the projector to the left/right of center. All it is is a little manual wheel that turns the lens to point in a different direction. I've never really noticed any distortion and never heard of anyone reporting any but I guess the picture can't be spot on if you're using it.

    Keystone correction on the Sanyo allows you to position the pj lower than the bottom of the picture. If the lens is pointing upwards you would naturally get a rombus shaped picture \____/. The Keystone allows you to electronically adjust the picture to make it straight |____|....just like you had the pj at dead centre.

    Z1 is now about 900 quid I think. Z2 out now or any day now.
     
  12. RTFM

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    Optical lens shift (Sim2, Sharp, Sanyo ) is very different from digital keystone correction which is best avoided as it does degrade the image.
     
  13. calscot

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    Lens shift does NOT produce perceptable distortion.

    Think about it - if it did then ALL projectors would be distorted as non lens shifted pjs are actually FIXED at FULL vertical lens shift (compared with the Z1), which would mean they had maximum distortion.

    It also has NOTHING whatsoever to do with keystoning.

    The Z2 is rumoured to have twice the limit of lens shift of the Z1. This would make it a very flexible machine with little need for keystoning at all. It has not been comfirmed yet.
     
  14. JUS

    JUS
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    lens shift will make the picture appear not straight..I would call that distortion.

    e.g. If you have your projector lower than the screen the picture will not be centred on the project screen. You then use lenshift to move the picture up. The screen is now on the screen but the bottom of the picture will be smaller than the top of the picture because the lens is nearer the bottom of the screen. The use of keystone fixes that. On the z1 keystone can't fix the distortion which occurs when you put the projector to the left or right of the screen.
     
  15. Woz!

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    I think you're wrong on this point.
    Lens shift on the Z1/Z2 does not distort the image, it merely repositions it on a flat plane. The PJ still needs to have its lens parallel to the surface onto which it's projecting, it can just move that image around (quite a lot as I understand it).

    You seem to be suggesting that it moves the image by pointing the lens in a different direction, and this isn't how it works.
     
  16. Kramer

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    Oh contrare :)

    Lens shift does move the lens so it's "pointing in a different direction" - eg. up/down or left/right.



    :smoke:
     
  17. nunew33

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    Click here for explanation

    By the way kramer I did get out of the right side of the bed, I was joking too, except my joke was funny!
     
  18. The Boogerman

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    Doesn't the Pansonic ae300 do horizontal or vertical (ie not both at the same time) keystone corrention?
     
  19. chris l.

    chris l.
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    For Info:

    Little video (german) of lens shift function on PLV-Z2.

    Regards,

    Chris
     
  20. chris l.

    chris l.
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  21. WeirdFish

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    So to conclude, lens shift doesnt distort the image.

    :)
     
  22. Chris Frost

    Chris Frost
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    :eek: Generally not recommended unless the projector is specifically designed for that use.

    Regards
     
  23. j05ha

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    Again, thanks for all your help! I had contemplated mounting the projector on its side but, amongst other things, it messes up your aspet ratio, and I then have the problem of mouting it dead center, erm, vertically, i think.

    So, it seems I'm down to Lens Shift or Horizontal key-stone.

    Lens Shift doesn't distort while key-stone would seem to offer more flexibility (ie I can mount further of center). The Lens Shift on the PLV-Z2 looks impressive (cheers Chris l.!)

    Looks like throw distance may also become a factor in my decision. hmmm there's more to this than meets the eye :)

    I'm going into London on Saturday (Totenham Court Road, here we come!) so I'll try a few and see which one works out. I'll post my findings!

    Thanks again.

    j
     
  24. nunew33

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    Jo5ha,
    If mounting off centre is to get a bigger image then another option is to mount the projector centre but project the image upwards and use a mirror at 45 degrees to reflect image on a wall. This might look a bit ugly but gets extra throw in a short room.

    Im not sure if all projectors can do this but the japanese brochure for the Sanyo Z2 shows this configuration.

    Here is the PDF brochure, look at page 4, labelled private room
     
  25. j05ha

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    I shouldn't have a problem with the throw distance as such I was just wondering if the it may affect how far to one side I can mount the projector. The key-stone effect increases as you move the projector towards the screen you see so I ws just thinking outlound as to how this might affect my positioning. I can feel an excel spreadsheet coming on!
     
  26. calscot

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    Jus, you have no idea about optics, do you? :rotfl:

    Like I said before MOST projectors have a fixed vertical lens shift which allows the picture to be above the height of the lens when the pj is upright and below when ceiling mounted.

    If you were correct then the only projectors to NOT need keystone correction would be the likes of the Sanyos at zero lens shift.

    Also if you were correct, ALL projectors would have increasing distortion to the edge of the picture as the edges have a fixed effective lens shift in comparison to the centre.

    Kramer, two people, near each other, pointing in a direction parallel to each other, are generally considered to be pointing in the same direction. Ergo a lens which has moved orthogonal to it's axis a centimetre or so is still pointing in the same ordinal direction. IE if it was pointing north 000' before it will still be pointing in the same direction after lens shift.

    To make it plain, the lens shift does NOT change the ANGLE of the lens.

    Any distortion comes from stuff like the fact that a lens is not hyperbolic as it should be, but instead uses a small arc of a circle as an approximation. The further from the centre of the lens you go, the worse that approximation becomes and therefore produces distortion.

    The compound nature of the lens to ensure other distortions are reduced eg chromatic aberration, will not work so well at off axis extremes either.

    Hope this clears things up.

    ps As the lens will be designed to have unnoticeable distortion at a distance of the screen height from the center, the Zanyo Z1 can have no more noticeable distortion than any other pj. As the Z2 which goes beyond this limit, it will have to have a lens which can cope.
     
  27. WeirdFish

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    Oh :confused:


    I was with you up until "To make it plain...."


    :rotfl:
     
  28. JUS

    JUS
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    calscot,

    Ok smarty pants :rolleyes: I'm keen to try and understand what you are saying here...

    "two people, near each other, pointing in a direction parallel to each other, are generally considered to be pointing in the same direction. Ergo a lens which has moved orthogonal to it's axis a centimetre or so is still pointing in the same ordinal direction. IE if it was pointing north 000' before it will still be pointing in the same direction after lens shift."

    Starting point: my lens is pointing north 000. I now change the len shift to move the picture two feet to the left. Are you saying my lens is still pointing north 000 ?

    Jus.

    P.S. Watching the vid it looks like the Z2 works differently to the Z1. When I lens shift on the Z1 my picture's shape changes.
     
  29. Draco10

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    jo5ha

    With regards projector choice,i"ve been using a Pany AE300 for a few months now and found it to be excellant for all sorts of use.The socketry on the back is more than ample for mosts needs be they Film(DVD,Laserdisc, VHS even gaming via the RGB equipt scart socket).There's also PC inputs which i use on a regular basis.The only caveats with this i find are having to increase your font sizes and not being able to view in full widescreen(only 4:3)because of picture distortion,but unles you've a dedicated widescreen video card i would assume you'll get this with any projector)correct me if i'm wrong).Computer wise i use a mac and manage to get XGA resolution.Which seems more than adequate.
    Gaming is something i've only just got into,computer games seem to pose no problems for the AE-300.Platform games seem easier to view probably because there's less movement going on,Driving games and shootem ups fair not so well(that's probably an age thing).When your 10ft away from a 7ft screen it becomes a bit intense.
    On a positive note though,you don't have to black the room out totally to get descent results.As long as you don't direct light onto the screen,i've found i have no problems(even with the lamp set to low power mode).
    If you're a true gamer,my advice is get a console(they are amazing!!!!!!!!).I borrowed a mates Sega Dreamcast and it is sooooooo much fun.Gaming on the big screen in the evening with your mates with a few bevvies can't be beaten.Saving up for the new X-BOX(as long as it's got RBG outputs you can't go wrong).
    Phew!


    With regards offcenter mounting:
    I've tried mine setup in various aspects,Ceiling table top and wall mount positions.
    Because the AE300 has both horizontal & vertical keystone correction which can be adjusted independantly,i found positioning not a problem,the short throw lens maybe though.My setup is as follows:
    Projector table mounted with lens approx 11ft from 92"diag (45"x80") screen with zero keystone adjustment and the manual zoom ring set to minimum the image fills the screen.The zoom ring could make it larger,but this is the minimal picture size for the distance used.This is fine if your wall space is able to cope with images of this size.
    You don't state how large you want to project,so this may suit you.(if in doubt,visit the Panasonic web site for spec sheets).
    I have been able to position the projector at either extremes of the room(11ft6")at this distance from the screen and(using the keystone adjustment)been able to get avery good resulting picture image.
    I know that picture degradation occurs and purists would throw up their hands in disgust,but the thing is keystone correction was invented to help you out when needed,so...if you can't get the perfect placement and you've found the projector you want...use it.If it wasn't supposed to be used,it wouldn't have been provided.

    As far as price goes(if you have'nt already) get a copy of Home Cinema Choice magazine and browse through the adverts.I managed to save a couple of hundred on the Pany by getting quotes from retailers and taking my HC Choice mag to a local Pany shop.I told them the lowest quote and they matched it,the money saved went towards an electric screen instead of a manual one.Best of all,i now have piece of mind(not buying a grey import)
    if it did go wrong i can just nip down the road and consult the dealer on my own home turf.
    With the imminent release of the PT-AE 500 you should have more bargaining power as they will want to move stock.

    Anyway goodluck with your search and i hope my ramblings have helped you out.
    http://www.avforums.com/forums/newreply.php?s=&action=newreply&threadid=102833#
     
  30. calscot

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    Jus,

    Maybe North was a bad example as we are on a circular plane on earth.

    So the answer is near as damn it yes. The only reason that the answer isn't 100% yes is that two parallel lines in a flat plane will not meet and therefore will not meet at the north pole. The angle would have to be slightly different for that to happen rather than the same.

    If you move the lens, the image will move the distance multplied by the factor of diffence in size between the image on the screen and the size of the image while passing through the lens.

    The picture will be projected on the same plane and so there will be no distortion with a perfect lens and no keystoning required. It will be pretty much the same as if you moved the projector to the right, but obviously by the distance moved on the screen rather than the lens movement.

    If you think about it this must be true. If you take the left hand edge of the lcd panel for instance. It is not in the centre of the axis of the lens, yet its light is projected in parallel with the centre of the lcd panel's light, giving an undistorted picture on the right hand side.

    Now supposing you move the lens so the centre is now effectively where the left hand edge was before, it will be no more distorted than the left hand edge was.

    As we have not said how far to the left the lh edge was, we can obviously extrapolate this and conclude that where-ever the left hand edge is now, it will not be distorted.

    You are basically just moving the picture right

    The limiting factor of this is obviously the size and quality of the lens as the further from the centre you go the more of a grazing angle you have from the lens and the limitations of the lens come into play. That is what limits how far you can lens shift.

    The Z2 is rumoured to lens shift by more than the Z1 and so either the lens is fine and can take it or they have changed the lens.

    It's very good news for people with high ceilings.
     

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