Not logged in
 
Jump to page: <<<12>>> (2 total)
Author
Topic: 12' ceiling mounted projector and trapezoid image
member
Joined: Oct 2, 2007
Posts: 2
Reply to PostAlert Moderator
I currently came into a position at a school district.

We have been installing dell projectors with Extron ceiling mount kits, but the problem is that when you have this mounted 12' in the air and 12' form the board and the board is mounted 4' off the ground you get a trapezoid affect on the board. Its wide at the bottom of the screen and narrow at the top....

What is this from and what can i do too fix this probolem, do i need to lower the projector down so its shooting a straight image to the board or is there some sort of adjusting that can be done...

Would greatly appreciate any support

thanks
moderator
Joined: Mar 28, 2005
Posts: 12,246
Reply to PostAlert Moderator
Think back to your own school days - remember the overhead projectors when the teachers would point them UP to hit the screen and you would end up with a trapezoid?

Same thing here - it is called keystoning.

There are two fixes for it:

1. (best) - Level the projector so it is perfectly horizontal, then move it to the correct height, usually a bit over the top edge of the screen (depends on projector), then project.

2. (worst) - Use digital keystone correction to digital compensate for the fact that you are tilting the projector downwards.

This issue is covered in the FAQs at the top of these forums and deals with the fact that you don't get to choose where your projector goes, the projector you BUY has a lens that has a fixed range where you can place it and careful consideration of this must be taken into account prior to purchase.
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
member
Joined: Aug 23, 2007
Posts: 45
Reply to PostAlert Moderator
Quote (AV_Integrated on Oct 2, 2007 9:52 PM):
This issue is covered in the FAQs at the top of these forums and deals with the fact that you don't get to choose where your projector goes, the projector you BUY has a lens that has a fixed range where you can place it and careful consideration of this must be taken into account prior to purchase.

I am dead serious when I say this. The comment above should be stickied for all of newbs to read. In our search for the best picture we (Joe 6 Packs, of which I'm included) also have a hard time mounting things from the projector to the screen. It is an absolute important fact to those who are new to this hobby understand it's not all plug and play when you decide to dedicate a room as a full time hometheater.
member
Joined: Oct 2, 2007
Posts: 2
Reply to PostAlert Moderator
I understand what you are talking about, but these are DELL projectors mounted a foot from the ceiling on a 12' high ceiling. The Promethean Board is mounted 3' off the ground, so the top of the board is at 7'. With that difference you have to tilt and or angle the projector to get an image on the screen. Within doing that the image is a trapezoid affect...

What projectors are available that you can mount high and aim low with a square image....
member
Joined: Aug 8, 2005
Posts: 4,417
Reply to PostAlert Moderator
This was already answered by AV_Integrated in so many words. But to answer the question directly, There are no projectors that can throw a square image mounted at 12' high if it is projecting onto a screen in which it's top is only 7' from the floor. I suggest either lowering the projector or raising the screen. Or do as AV said and use keystone, but even then it may be too steep of an offset even for kesytone.
[Edited by Natja-ss-1334 on Oct 3, 2007 at 3:02 PM]
Experienced with Yamaha Dpx-830sl, Mitsubishi HC1500, Infocus SP7210, Optoma HD80, Optoma H78DC3, Optoma H27,Optoma H31, BenQ 6100,Infocus 4805, and many others.
Jump to page: <<<12>>> (2 total)