Projector Lens Shift and Layout Planning

Discussion in 'Displays' started by Jay Mitchosky, Mar 31, 2003.

  1. Jay Mitchosky

    Jay Mitchosky Producer

    Joined:
    Sep 6, 1998
    Messages:
    3,729
    Likes Received:
    0
    Hey All

    It's a toss up whether or not this could be located here or in display devices...

    Working on the layout and details of my pending HT construction and have run into a snag with projector positioning. I am considering the Sharp XV-Z10000U projector (with a 96" wide 16:9 Stewart FireHawk screen). The predominant recommendation for projector placement (on the vertical plane) is to have the center of the lens line up with the top of the screen (I am ceiling mounting). The screen will be placed such that my eyes are lined up 1/3rd from the bottom, which places the top of the screen (and hence the center of the projector lens) at 19" from my 8' ceiling. Not happy with the way that will look hanging out into space - be it an 8' or 80' ceiling it's going to be constrained by the screen position.

    Here's where I'm confused. The Sharp includes an optical lens shift, which if I understand correctly allows you to compensate for vertical positioning up to one screen height with the projector placed anywhere between the top and bottom of the screen without having to employ digital keystone correction. What precisely is the benefit of this feature? I would imagine the goal of a lens shift would be to allow you to place the projector higher than the top edge of the screen (for ceiling mount) and then shift the image properly onto the screen plane - thereby keeping the projector up and out of the way.

    Given that you are able to shift the image down while lined up with the top of the screen, why can you not have the projector elevated above and shift to the "normal" position? You would obviously not be able to cover the same range on the screen, but what value is there is moving the whole image below center anyway? What experience has everyone here had in their projector installations?
     
  2. Jay Mitchosky

    Jay Mitchosky Producer

    Joined:
    Sep 6, 1998
    Messages:
    3,729
    Likes Received:
    0
    Going to try this in Display Devices...
     
  3. mark alan

    mark alan Supporting Actor

    Joined:
    Nov 19, 2002
    Messages:
    620
    Likes Received:
    0
    I am not sure what you are asking. The main purpose of the lens shift (in my opinion) is to allow you to slighly adjust your picture in order to exactly center your picture on the screen without degrading the image using a digital correction. That way, if you are a little off on your screen or mounting placement, you can still get the picture exactly right.

    When I set up my Z1, I thought that I measured all my dimensions exactly, and I wouldn't have to shift my lens all the way down. Of course, I ended up using all the shift. Without it, though, I would have had to redo everything.

    I don't see anyway you can have a projector which is flush against the ceiling and projects an image which begins two feet (or whatever) below the ceiling without sending the light at an angle and distorting the image. You either have to have the screen against the ceiling or accept that the projector will hang down from the ceiling. My ceiling in the basement is only a little over seven feet high, so I hung my projector on a wooden platform with chains. I lower it to use, and raise it up against the ceiling when it is not in use.
     
  4. Doug_B

    Doug_B Screenwriter

    Joined:
    Feb 11, 2001
    Messages:
    1,081
    Likes Received:
    0
    Jay,

    I think you're out of luck with the Sharp. From my readings at AVS, it is true that the Sharp needs to be vertically between the top and bottom of the screen for its lens shift to work. However, a possible alternative to digital keystone correction may be tilting the projector and screen enough so that the projector "thinks" it's in line with the top of the screen (and perpendicular to the top). I do agree with you that there is added value in supporting a lens shift where the lens is vertically higher than the top of the screen. My Infocus 7200 does just that; however, it supports only a fixed vertical offset.

     
  5. Jay Mitchosky

    Jay Mitchosky Producer

    Joined:
    Sep 6, 1998
    Messages:
    3,729
    Likes Received:
    0
     
  6. Doug_B

    Doug_B Screenwriter

    Joined:
    Feb 11, 2001
    Messages:
    1,081
    Likes Received:
    0
     
  7. Rob Tomlin

    Rob Tomlin Producer

    Joined:
    Jan 8, 2000
    Messages:
    4,505
    Likes Received:
    0
     
  8. Jay Mitchosky

    Jay Mitchosky Producer

    Joined:
    Sep 6, 1998
    Messages:
    3,729
    Likes Received:
    0
     
  9. Rob Tomlin

    Rob Tomlin Producer

    Joined:
    Jan 8, 2000
    Messages:
    4,505
    Likes Received:
    0
     

Share This Page