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Best Position Optically For Projector

Discussion in 'Projectors, Screens & Video Processors' started by charles, Nov 7, 2004.

  1. charles

    charles
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    I have on order a Sony HS50 projector.This has a 1.55X zoom lens with a 100" diagonal image being achieved from a throw rate of between 9.5Feet to a maximum of 14.7 feet. What would be the best position for the projector
    A. Ceiling Mounting
    B.Shelf Mounting
    C.Coffee table.
    I shall be using a 7foot 16X9 screen fixed to the wall
    Also any recommendations for fixed screens
    Thanks
    Charles
     
  2. KraGorn

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    For any projector I'd have thought the best position is when the image fills the screen without the use of lens shift or keystone adjustment, whether it's the right-way-up or upside-down shouldn't make any difference as long as the optics are uniform.

    If the projector has an image offset, ie. the centre of the lens isn't the central poit of the projected image then that has a bearing on its' positioning, I can't quickly check if the HS50 has such an offset.
     
  3. Oakleyspatz

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    If you can, ceiling mount it . Once set up correctly, you won't need to touch it again unlike a shelf or table where it can be moved and will need constant re-aligning, focusing etc. Most, if not all current home-cinema projectors have a ceiling mount option which basically flips the image so when upside down it shows right way up. This is not the same as keystoning and does not alter the shape of the image. Mount the projector first, centrally and pointing parallel with the ceiling to the wall, then place the screen to align with the image rather than trying to move the image to fit the screen which can compromise the image's integrity.

    Hope this helps.
     
  4. LV426

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    Broadly speaking, projectors typically are best mounted either

    a) right way up, with the lens about level with the bottom of the screen OR
    b) upside down, with the lens about level with the top of the screen

    and in either case, with the lens laterally aligned with the centre of the screen.

    Lens shift, if fitted, can offer some flexibility in this. Digital keystone correction (or side shift etc) can, too, but this does degrade the image somewhat and is best avoided if possible.

    Ceiling is probably least obstrusive and most convenient.
     
  5. charles

    charles
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    Thanks for your reply. This may seem a stupid question but is there a recommended height that a 6 or 7 foot 16x9 screen should be from floor level?
    I shall be viewing from 13 -14 feet away from the screen. Thanks .Charles
     
  6. Darwock

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    Whatever's comfortable I guess, you don't want to get a sore neck!
     
  7. LV426

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    Ideally, the vertical middle of the screen broadly level with your eye position. However that's often impractical and a little higher won't cause grief.

    Another way of looking at it is to say, given a ceiling mount for the projector that is both aesthetically acceptable when it's not in use, and won't be so low as to get caught as you walk underneath, how far down is the lens from the ceiling? This measure gives you the right position for the top of the screen.
     
  8. jamiev

    jamiev
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    the best place for it is central to your screen using no keystone correction.prob the right way up on a high shelf.
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Jamiev: If there is any lens offset (which it is likely there will be) then your suggestion is impossible. With no offset then you are correct.

    Gordon
     
  10. Ekko Star

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    :smashin: That's how I have mine.....

    Yep, sure do ! Slap bang middle of the picture. It's a lovely experience looking straight on and being almost immersed into a 9ft picture. Wouldn't have it an other way :)
     
  11. danjos

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    Im with jamiev on this one, i dont understand why some people suggest ceiling mount is the 'best' way to go?
    I have mine shelf mounted so the projector is aligned with the centre of the screen (tx100, fires centrally) so i need no keystone, lens shift or zoom. I thought this would be the best setup possible? surely ceiling mount requires some correction to achieve a flat squared picture?
    The shelf is fairly high up the rear wall so the projector never gets moved. I do find that when replacing the lens cover it sometimes slightly adjusts the focus wheel (unavoidable on tx100) but this slight hassle would be compounded with a harder to reach ceiling mount.

    Just my opinion :)
     
  12. Ekko Star

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    Probably cos it's simply out of the way up there. But any PJ prone to dust problems can be a pain.

    Bear in mind nigel's principle's and you are on the right track. I you have it high up on a shelf the PJ has to be upside down and also take into account the offset.
     
  13. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    As zero offset lens in PJ's are pretty rare in my experience and with such a system you would often find yourself with a PJ in front of your face or firing in to the back of your head it's quite easy to understand why you would ceiling mount.

    You want no keystone as electronic keystone will reduce resolution and will probably lead to artefacts. If the lens assembly in the PJ has an offset because it was designed for table or ceiling mount then sticking it in middle of screen would mean you need to add lots of keystone(bad). As the angle of incidence=angle of reflection you would probably find that if you ceiling mount and sit in correct place the most light actually gets reflected at you rather than over your head etc.

    So it should be obvious that the reason different folk suggest different things is because the ideal mounting is dependant on the PJ and the seating arrangements/screen.

    Gordon
     
  14. moco

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    It also depends on the type of furniture the audience will be sitting/lying on.
    If you sit on recliners or lie down on a bed/futon with raised back, you would want the screen higher up than if the audience sits straight up as in a theatre.
     
  15. danjos

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    hmm, you shot jamiev's idea down pretty quick without knowing anything about 'seating arrangements/screen'
     
  16. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The seating position is irrelevant with jAMIE's suggestion. If there is any lens offset you can't place the PJ in that position, so why mention it. I also think if you re-read the post I don't "shoot him down in flames" but rather point out he is correct in one scenario and wrong in another.

    I agree I could have been more thorough in my reply however. Would it have been better to say nothing and wait for someone to place their PJ in the position recommended then come on here asking why the picture didn't fill the screen and it looked crap..........

    You state yourself that you cannot understand why folk make recommendatons they do so I explained possible reasons why.

    Gordon
     
  17. LV426

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    Just to re-inforce what Gordon says:

    The majority of home theatre projectors have a lens offset built in. This means that (mounted right way up and horizontally - not tilted) they fire the bottom of the image horizontally and the top of the image upwards.

    Mounted upside down, they fire the top of the image horizontally, and the bottom downwards.

    Hence my (and Gordon's) assertions. If. of course, the projector you have or buy has no offset (as might be the case with some types of data projector) then central to the screen in both planes is the correct position.
     
  18. MikeRJ

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    Not at all. Most (but not all) projectors have some built in image shift so the lens is typicaly pointing more towards the bottom of the projected image rather than the center. This means the projector can be mounted on a level surface wether it it on a coffee table etc (projector right way up) or on a ceiling mount (projector upside down).

    Mounting the projector the right way up on a high shelf would cause most of the image to be on the ceiling, unless the shelf was sloping dangerouly downward, in which case you'd probably get focus problems accross the image. No amount of seating arrangements alters that basic fact.
     
  19. Ekko Star

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    Everyone has different seating arrangements and layouts but the original question is best place for the PJ optically.

    When you are sat down, your eyes 'should' be level with the centre height of the screen or image projected. This holds true for many a display device. Of course not everyone can manage that set up or desire it that way in their rooms.

    But the question has asked the "best optically" and that would have to naturally relate to the best viewing wise as well.

    I can't advocate pro-longed lying down or looking up at an image as it induces neckache for me, but heh different strokes for different folks. :thumbsup:
     
  20. William

    William
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    Like the AE700 and Z3, the HS50 has lens shift which is set up with no offset. This means that the centre point of the shift is with the lens in line with the centre of the screen. All the reviews I have seen of these projectors recommend minimising the lens shift with the "sweet spot" being the lens in the mid position. This uses the most optically efficient part of the lens and minimises distortion and colour fringing.

    Older fixed lens projectors (like HS20, AE500) had an offset built in to allow ceiling mounting I don't know whether they were designed to use the most efficient part of the lens or whether they were infact inherently not ideal. If it was the former then the introduction of lens shift may be a backward step in quality if, as with most setups, you can't mount the projector in line with the centre of the screen.

    I must admit it does seem stupid to introduce lens shift and then recommend not using it (fully)
     
  21. danjos

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    gordon, i was assuming that all projectors with optional lens shift (which is most newer models) will not have any built in offset, ive never really thought about it though, just occuring to me that maybe im wrong about that, so i see where your coming from now. also i didnt read the posts very thoroughly.
     
  22. Gordon @ Convergent AV

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    If you have lens shift then I'd expect no offset. As you go to extreme of lens shift you do risk adverse effects on image but 'd suspect most manufacturers will not allow you to go far enough to distort/crop or otherwise damage image in this way.

    If the HS50 is a lens shifting PJ then I'd go for mid screen or just above if you'll be looking up at screen.

    G
     

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