Have Acer H6510BD, thinking should have went BenQ W1070 due to lense shift :/ - AVS Forum
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post #1 of 9 Old 07-01-2013, 10:59 AM - Thread Starter
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I am new to projectors and obviously didn't do my homework long enough before ordering the Acer to save hundred or two, thinking they were pretty much the same. I'd return it, but then I have to pay a ridiculous re-stocking fee, shipping, etc. The Acer is still in the box, I am going to mount it on the ceiling, it's a low basement ceiling, maybe 8ft., so flush mount would lover the projector less than a foot below the ceiling. My screen is 100", and it's about 2ft. below the ceiling. So reading about this lense shift, my projector doesn't have it... and it won't be positioned center of the screen, so I'm a bit worried. The H6510BD will be mounted upside down, and the mount tilts down some so I can point it toward the screen. I don't know what to expect, I am thinking I might have a slight trapezoid image displayed?!?! I am hoping that due to the fact it's mounted upside down and the angle isn't that significant I can get away with it. If anyone can put my mind at ease or give me some pointers I would appreciate it. I was not sure if placing it a few feet closer or a few feet further than the recommended distance would help, but I have that option, it's just height that I don't have a lot of flexibility. I attached a sketch of pretty much how it will be angled and displayed, so any input at all would be appreciated. I have heard a little about keystone correction, that it isn't ideal because picture quality suffers to a degree, but would this be an option be for me? Thanks for any advice, ideas, or anything. projector.JPG 9k .JPG file
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post #2 of 9 Old 07-01-2013, 11:12 AM
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Is it possible to shelf moutn it behind you center of the screen?

If not you will need to use Digital keystone correction to fix the "trapazoid" effect which will work but will degrade the image a bit.

Placing it further away from the screen at less of an angle will help with the severeness of the angle its projected at however it will need to be mounted center of the screen to avoid any quality issues.

I was looking at MAYBE picking one of these up and it would be placed on a shelf basically above my head (couche is against the wall)

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post #3 of 9 Old 07-01-2013, 11:26 AM - Thread Starter
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Thanks, and unfortunately it's not at all possible, seating is kind of a bit farther than I want it to be already, and the room is quite long, it's pretty much a giant rectangle the length of the house so there's actually back to back couches, each one facing opposite sides of the room. I am wondering now if I should bite the bullet, don't even open the box, try to sell it on eBay or something then pick up the BenQ. The restocking fee is 15% plus shipping, so it would cost me over $100 just to send the damn thing back unopened :/
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post #4 of 9 Old 07-01-2013, 11:57 AM
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I may be wrong but what i get from the Acer calculator is your projector needs to be about 9 1/2 feet from the screen (for 100") and the center of the lens 6" above the top of your screen so you would need to mount the projector lower or raise the screen. I only have a 7'8" ceiling in my basement but between adjusting the height of either the screen or projector I've made it work with several different projectors over the years. You really don't want any tilt.
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post #5 of 9 Old 07-01-2013, 12:26 PM
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Quote:
Originally Posted by terry2 View Post

I may be wrong but what i get from the Acer calculator is your projector needs to be about 9 1/2 feet from the screen (for 100") and the center of the lens 6" above the top of your screen so you would need to mount the projector lower or raise the screen. I only have a 7'8" ceiling in my basement but between adjusting the height of either the screen or projector I've made it work with several different projectors over the years. You really don't want any tilt.

I'm pretty sure this particular projector is a straight thorw, no offset.. I could be wrong though

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post #6 of 9 Old 07-01-2013, 12:40 PM
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According to the Acer site (don't have one so just going by what I found)....

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post #7 of 9 Old 07-01-2013, 01:42 PM
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Yes, you will have trapezoidal image if no corrections are made. Digital keystone correction will be scaling the image, resulting in potential loss of sharpness and occasional visual artifacting (often not noticeable, depends on how picky you are).

Sounds like the amount will be pretty slight though -- the lens centerpoint is about 3" below the top (when ceiling mounting) on that projector if I remember correctly, and the offset will be about 5-6 inches. So the 'best' location for your screen would be around 8-9" below the ceiling. Your screen is 24" below the ceiling, so 15" too low.

Now, you've got 113" throw distance, and your error is 15", so that's tan^-1(15/133) = ~7.5*

So assuming you won't return the projector you have 5 options:

-Digital Keystoning
-Trapezoidal display area
-raise your screen 15"
-lower your projector 15"
-Angle your screen to match the projector angle. Basically, if you move the bottom of your screen out away from the wall about 6-1/2", your screen will now match the angle of the projector. There's still a suboptimal viewing experience since the screen will not be perpendicular to the viewers, but I personally did this once and found the result OK. I think in my case it was about 6* (compared to your 7.5*) and I could definitely tell there was a tilt, but it never really bothered me. This is a subjective thing, however, so ymmv.





*EDIT* actually less than 6-1/2", even if you've got a flush mount, there will be some drop from the ceiling, probably another 5" or so. So you're probably more like 10" too low instead of 15" --- which would be closer to 6* angle, which would need more like 4-3/8" spacing from the wall on the bottom.


Math behind this is pretty simple, basically the ratio of the offset "error" to the distance you're projecting should equal the ratio of the bottom spacers to the total screen height.

In other words, if there's 10" error, E/113 == X/49 where E = error and X = screen bottom spacing. So if E = 10, (10/113)*49=4.33628..... (around 4-3/8)

The error is how far below "perfect" your screen is.
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post #8 of 9 Old 07-02-2013, 10:14 AM - Thread Starter
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Thank you both for your replies. Defiancecp, those numbers you gave me were very useful and I am going to have to measure things more closely when I get home today. I may have inaccurately estimated my screen being 24" below ceiling, it may actually be less, possibly half that. So as you said, it may be a very slight imperfection. The screen lowers right under the wood awning (not at home right now, but I had this pic on my phone), and the mount I have has three positions. The problem is, with even the middle extension, it sits so low that it's extremely awkward and distracting when it's in front of the screen seeing my seating is further back. You also have to kind of walk around it because unless you're 5' 2" you're gonna run into it. I may give it a shot flush mount and see how bad it is. Or I may modify the mount and trim the extension pole so that it doesn't hang so low. Is the 9.5' throw set in stone, could I place it further away, like 10-11'? Angling the screen outward as you said might be hard seeing it's a motorized screen, I'd have to run over there and pull it out somehow every time I lower it, so I'd like to try and avoid that scenario. Thanks again for your help and all the calculations.



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post #9 of 9 Old 07-02-2013, 02:35 PM - Thread Starter
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Just got home and measured, the screen is 8, 8.5" down from the ceiling. I'm thinking of mounting the projector about 10.5 feet away from the screen and doing it flush with the mount. The mount lowers it down a a few inches, so the lense centerpoint will be that much lower. I'm gonna give it a shot unless I can come up with a better way, but I think I might be good. This is all new to me but it's really cool stuff. Just installed my custom wall plate and will be stringing vga, hdmi, composite, component, 3.5, usb, etc. all night. But I wanna have that baby up and running Avatar this weekend. It's so frustrating having everything I need but it just takes time and work and research. The audio I got down but that was a job as well. Thanks again for all your advice and any other ideas I'm all ears!!
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