# Projector placment...?



## jstanley214 (May 22, 2013)

My ceiling is 8 ft tall and I'm projecting about 15 ft away from the wall. How low does the projector need to be from the ceiling to prevent the need of using a keystone adjustment? I've heard using keystone will cause you to loose screen size and I don't want that to happen. The projector is going on a shelf that I'm going to install on the wall. Any help is GREATLY appreciated. I'm a total noob to this!


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## tonyvdb (Sep 5, 2007)

It needs to be placed even with the top of the screen or lower in order to avoid using keystone. Most projectors will have some lens shift capabilities so there may be some flexibility


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## jstanley214 (May 22, 2013)

My issue is that currently I put the shelf a little too high I think which caused half of the image to be on the ceiling. I had to put something under the back of the projector to fix that thus causing a keystone adjustment. I didn't want to bring the shelf down much further in fear of it being too low and just not looking right but I may have no choice.


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## Mike Edwards (Mar 10, 2011)

jstanley214 said:


> My issue is that currently I put the shelf a little too high I think which caused half of the image to be on the ceiling. I had to put something under the back of the projector to fix that thus causing a keystone adjustment. I didn't want to bring the shelf down much further in fear of it being too low and just not looking right but I may have no choice.


ok, if you're on a SHELF, that means the projector is sitting on the feet. and a projector naturally shoots "upwards" meaning you'll have to really drop the pojector a good chunk to get it even with the screen. if you have it up high it's meant to be flipped upside down and hung from a ceiling mount so it would then shoot "downwards".


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## jstanley214 (May 22, 2013)

So maybe mounting it underneath the shelf could resolve the issue. I'll give that a shot this afternoon when I get home from work.


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## RBTO (Jan 27, 2010)

Sorry, but you won't gain that much. If you have a projector without lens shift, the center of the image will be at the level of the projector (when the projector is true and level) no matter what (drop the position of the projector 1 foot, and the image drops 1 foot). The only way to address your situation is to tilt the projector (as you've done), or to use lens shift. If you want an image without the need for keystone correction and you don't have lens shift, then the projector needs to be at the level of the center of the screen.

When you tilt a projector, you'll _always _get keystone distortion unless you tilt the screen so it remains perpendicular to the projector beam axis (a line drawn straight out from the projector lens). Correcting that with the projector (electronic keystone adjustment) will introduce some image quality issues, and you may have some brightness fall-off problems if the tilt is large enough.

With lens shift, the image is moved without any keystoning, in both the vertical and horizontal directions so it can be recentered on an off axis screen without image or brightness issues. Some projectors have more lens shift range than others. I assume your projector doesn't have this feature so you're stuck with tilting and (keystone) correcting. The amount of tilt required determines how much keystone correction you'll need, and your projector will determine if you can get that amount. If your projector is limited in its keystone correction, you may end up with some keystone regardless.

Panasonic projectors (and others) have lens shift which is fortunate because I have an application where the projector is not only at ceiling height, but also off to the side of the screen. My Panny still allows a "curved ball" so to speak, so the screen image is right on even from that skewed angle, without any keystoning to worry about.


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## jstanley214 (May 22, 2013)

Yeah I'm having to use quite a bit of keystone adjustment. It's currently set at 13. The picture looks good but the issue is this trapezoid black square around the image. It didn't bother me at first but now my eyes have adjusted and its driving me crazy. I've got an Optoma HD65. I believe there is no lens shift. There is only image shift. I am able to shift the image down some off the ceiling but once you reach a certain point, you start to loose some of the image at the bottom where there would be subtitles in some movies.


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## Mike Edwards (Mar 10, 2011)

jstanley214 said:


> Yeah I'm having to use quite a bit of keystone adjustment. It's currently set at 13. The picture looks good but the issue is this trapezoid black square around the image. It didn't bother me at first but now my eyes have adjusted and its driving me crazy. I've got an Optoma HD65. I believe there is no lens shift. There is only image shift. I am able to shift the image down some off the ceiling but once you reach a certain point, you start to loose some of the image at the bottom where there would be subtitles in some movies.


honestly, unless you want to put the projector on a coffee table in front of you I'd say it's time for a ceiling mount with a drop down pole


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## jstanley214 (May 22, 2013)

I've thought about that too but can't do that right now. I'm good with dropping the shelf some more. I could probably go about another 5 inches down. At least if I had to use keystone still, it wouldn't be nearly as severe as it is now.


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## RBTO (Jan 27, 2010)

jstanley214 said:


> I've thought about that too but can't do that right now. I'm good with dropping the shelf some more. I could probably go about another 5 inches down. At least if I had to use keystone still, it wouldn't be nearly as severe as it is now.


One other thought that might help - you could construct a periscope adapter for your projector that you put in place just when you use the projector. You'd need two first surface mirrors, one a bit larger than the lens, and the second, considerably larger. These would shoot the projector beam downwards (45 degree angles on both mirrors) to a point in line with the screen center, then no keystone correction would be needed. When the movie's over, just put the periscope away. A bit of a job but not too hard if your handy at woodworking.


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## 86eldel68-deactivated (Nov 30, 2010)

> My ceiling is 8 ft tall and I'm projecting about 15 ft away from the wall. How low does the projector need to be from the ceiling to prevent the need of using a keystone adjustment?


According to ProjectorCentral.com's Projection Calculator for the Optoma HD65, the smallest 16:9 image you can throw from 15' is 122", and to get that centered onto a screen the mid-point of the lens has to be 11" above the top of the actual screen (and not above any border that might surround the screen).


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## RBTO (Jan 27, 2010)

eljay said:


> According to ProjectorCentral.com's Projection Calculator for the Optoma HD65, the smallest 16:9 image you can throw from 15' is 122", and to get that centered onto a screen the mid-point of the lens has to be 11" above the top of the actual screen (and not above any border that might surround the screen).


If you have a full 122 inch diagonal, that gives your screen a 60 inch height so if the very top is flush with the ceiling (which it probably isn't), the projector would have to be 30 inches (60/2) below that to have a keystone-free image. If the top of the screen is 6 inches below the ceiling, add 6 inches to come up with 36 inches below ceiling level for the projector. Bottom line is that the lens of the projector must be centered on a line extended from the _center_ of the screen (perpendicular to the screen surface) to obtain a keystone-free image. There's no relevance to the _top or bottom_ of the screen other than the projector must be located half-way between them.


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## 86eldel68-deactivated (Nov 30, 2010)

> Bottom line is that the lens of the projector must be centered on a line extended from the _center_ of the screen (perpendicular to the screen surface) to obtain a keystone-free image.


That is incorrect.

Projectors such as the OP's Optoma - and my previous InFocus SP7210 - have a fixed, angled throw, and you have to place the projector at a set distance above the top or below the bottom of the screen in order for the image to be thrown perfectly onto the screen.

Keystone correction only comes into play if your PJ is at a point other than the recommended distance above or below the screen and, in order to compensate, you have the projector physically tilted upward or downward to center the image onto the screen.

OP, here's how it works:
- Using 122" (diagonal) as the size of the image you're throwing, you have an image height of 60".
- If the center point of your PJ's lens is 8" down from the ceiling, the top of the screen should be 19" from the ceiling.
- If your screen happens to be, say, 26" from the ceiling, you'll need to drop your PJ by another 7" inches (so that the center point of the lens is now 15" from the ceiling).

(NOTE: The screen refers to the screen material itself. If you have a fixed-frame screen with a 3" black border, ignore the border - that is, don't measure from the center point of the lens to the top of the black border.)


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## jstanley214 (May 22, 2013)

Thanks for all of the information everyone. I really appreciate the help. It's all starting to make more sense now. It looks like I will just need to drop the shelf a few inches. I don't have a screen yet. I'm going to build one in the next couple of weeks. I can't wait to fix this issue. With the amount of keystone I'm currently using, I'm loosing about 10 to 12 inches of screen size. I measured the distance last night again and I'm actually projecting about 13 feet back.


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## 86eldel68-deactivated (Nov 30, 2010)

Be sure to use the calculator to determine the exact offset (center point of lens to top of screen) that you need, based on i) your throw distance and ii) the diagonal size of the image you're trying to project.


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## RBTO (Jan 27, 2010)

eljay said:


> That is incorrect.
> 
> Projectors such as the OP's Optoma - and my previous InFocus SP7210 - have a fixed, angled throw, and you have to place the projector at a set distance above the top or below the bottom of the screen in order for the image to be thrown perfectly onto the screen.....................


So what you're saying is that the OP's Optoma and the InFocus have built-in _fixed lens shift_. I was referring to projectors _without_ lens shift. I do however stand corrected in the cases you're mentioning in that they wouldn't need to be aligned on-axis, and that certainly helps in the OP's case.

Now, what a previous poster mentioned about mounting the projector upside down makes sense. With a fixed lens shift, it would definitely make a difference between shooting from the ceiling level or shooting from a table below screen level. 

Sorry, I wasn't aware this was a feature in the OP's projector.


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## 86eldel68-deactivated (Nov 30, 2010)

> So what you're saying is that the OP's Optoma and the InFocus have built-in _fixed lens shift_.


Not so much a fixed shift as a fixed - but angled/offset - throw.



> I was referring to projectors without lens shift.


If a PJ doesn't have lens shift, I think it normally has an angled/offset throw. But where it would have neither, then you are correct that the lens would have to align with the center point of the screen. 



> Sorry, I wasn't aware this was a feature in the OP's projector.


No worries.


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## jstanley214 (May 22, 2013)

Well I lowered the shelf this week and am very pleased. I gained about another 5 inches in screen size so I'm finally at 100" screen size. I still have to some keystone adjustment but the setting went from 13 to 3. I also started building my own screen this weekend. I'll probably have it finished this next weekend.


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## jstanley214 (May 22, 2013)

Well my final projection size is now 102". Built a frame today and now it looks insanely good! I love it!


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## Mike Edwards (Mar 10, 2011)

jstanley214 said:


> Well my final projection size is now 102". Built a frame today and now it looks insanely good! I love it!


what material are you building the screen out of ?


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## jstanley214 (May 22, 2013)

I used 1 x 3 pine wood and wrapped it in black fabric. The fabric is like a Cotten/velvet material.


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## Mike Edwards (Mar 10, 2011)

jstanley214 said:


> I used 1 x 3 pine wood and wrapped it in black fabric. The fabric is like a Cotten/velvet material.


lol, I'm sorry, I meant the screen material itself, not the frame and trim material


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## jstanley214 (May 22, 2013)

I'm projecting on the wall for now. My wall is flat. I may eventually go to a photo store and get some of the material that's used for back drops. That's what I hear you should use.


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## snickers1 (Jun 26, 2013)

you want avoid using keystone does your projector have the manual lens shift? my ceiling is also 8 ft and i used a 9inch drop rod and the screen is about 13inch down from the ceiling so with the mount and drop rod i am about inch above the screen i think give or take. if you have a 2:35 format screen and plan on using lens memory for 16:9 and 2:35 format movies it will never work if you use any keystone at all.


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## jstanley214 (May 22, 2013)

I am still using some keystone still. Not near as much though. I am projecting a 16:9 aspect ratio. There was still some border around the image as a result of the keystone, but the frame has taken care of that.


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## jstanley214 (May 22, 2013)

Oh yeah and my projector doesn't have lens shift.


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