Help w DIY Sintra screen, multiple issues - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 9 Old 04-25-14, 08:25 PM Thread Starter
Shackster
 
Join Date: Nov 2013
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Help w DIY Sintra screen, multiple issues

Hi All, I hope I'm posting this in the rights place. Here goes.

I've run into a couple of snags with my screen/projector set-up.

1. I've run into an issue with aligning the projected image with my screen. I've sketched a quick picture of the problem, as can be seen the top and bottom left corners are square but the left and side of the image slants inward from the top to the bottom right corner. I've been trying to find that perfect sweet spot for the passed 3 days, even remounted my screen higher on the wall but still can't get the image perfectly square on the screen. Before re-mounting the screen to the wall I taped out the borders and squared them, then using a grid and also a checkerboard test pattern aligned the image so the grid squared with the tape. After having achieved a square image i marked the top edge then remounted my screen. I Then adjusted the zoom on the PJ but could not square the corners without having any light spill.

https://drive.google.com/file/d/0B1U...it?usp=sharing

2. I'm using a 48"X86" 6mm thick sheet of Sintra board glued to a 1" poplar frame set about 3" inside from the edge of my screen and an 18" french cleat to give me some horizontal movement for image alignment. when projecting an image onto the screen, however, the bottom edge of the image curves lightly up towards the center of the screen leaving a 1/4" gap be tween the bottom of the image and the edge of the screen. Upon further inspection I've come to find that my screen is slightly convex, like an inverted curved display. Any suggestions on how I might be able to re-enforce the wooden frame to eliminate this curve?

Some additional pictures I've taken as I've worked. Sorry for the poor quality, the camera on my phone can't handle the lighting in my place.

https://drive.google.com/file/d/0B1U...it?usp=sharing

https://drive.google.com/file/d/0B1U...it?usp=sharing

https://drive.google.com/file/d/0B1U...it?usp=sharing

https://drive.google.com/file/d/0B1U...it?usp=sharing

Last edited by Harpmaker; 04-26-14 at 01:59 PM. Reason: Show image links
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post #2 of 9 Old 04-26-14, 01:57 PM
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Don
 
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Re: Help w DIY Sintra screen, multiple issues

OK lets see if we can get those images to show up. Hmmm, it seems that you can only go to Google Drive to view those files. I'll edit your post so the links show up and folks can click on them to view them.

Sorry, I have no recommended fixes for your problem at the moment. Was the Sintra sheet not flat when you got it?
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post #3 of 9 Old 04-27-14, 01:39 PM
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Re: Help w DIY Sintra screen, multiple issues

Quote:
b18un wrote: View Post
Hi All, I hope I'm posting this in the rights place. Here goes.

I've run into a couple of snags with my screen/projector set-up.

1. I've run into an issue with aligning the projected image with my screen. I've sketched a quick picture of the problem, as can be seen the top and bottom left corners are square but the left and side of the image slants inward from the top to the bottom right corner. I've been trying to find that perfect sweet spot for the passed 3 days, even remounted my screen higher on the wall but still can't get the image perfectly square on the screen. Before re-mounting the screen to the wall I taped out the borders and squared them, then using a grid and also a checkerboard test pattern aligned the image so the grid squared with the tape. After having achieved a square image i marked the top edge then remounted my screen. I Then adjusted the zoom on the PJ but could not square the corners without having any light spill.
Have you considered lens' offset when mounting? Projector's brand and model?

The underline part shows that the problem is not coming from the projector but from the installation.

Possible causes:

Lens offset
Your wall is not dead vertical on each side or not parallel with the opposite wall.


You can use a laser beam or a piece of rope to chech this out. From projector's lens have the rope touching screen's four edges. If it is perfect, the distance will be equal to both sides.
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post #4 of 9 Old 04-29-14, 11:41 AM Thread Starter
Shackster
 
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Re: Help w DIY Sintra screen, multiple issues

Thanks Harp, is there a better image hosting site I could use? As to the Sintra, it lays flat when placed on the floor but there still seems to be a slight curve to the sheet when hung from the wall. Last night I added some cross pieces to the frame to give it more stability and the sheet now hangs vertically even across the whole surface. Now I just need to figure out if it's even horizontally. Sorry for the delayed reply.

Last edited by DIYADD; 04-29-14 at 12:32 PM.
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post #5 of 9 Old 04-29-14, 11:50 AM Thread Starter
Shackster
 
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Re: Help w DIY Sintra screen, multiple issues

Thanks Yainnis! Sorry for delayed response. The top edge of my image is 8" below the center line of my projectors lense, is this what the offset is? The wall is vertically level. I will try the rope trick when I get home tonight.
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post #6 of 9 Old 04-29-14, 12:29 PM Thread Starter
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Re: Help w DIY Sintra screen, multiple issues

Update

So after further investigation I discovered that my sintra sheet was not hanging vertically level even though the wall it is hung on is. I also discovered the screen was not vertically even *facepalm*. Part of the problem was the French cleat creating a space between the screen's frame and the wall and part of is was the frame being insufficient to evenly support the Sintra sheet. The space between the wall was solved with some adhesive felt pads (like those used on the bottom of furniture). I've added two vertical supports to the inside of the screen's frame and that has solved the issue of the screen being vertically even.

My next step is to try and determine if the screen is horizontally even. I held a 6' straight edge up to it last night and couldn't find any curve, but the bottom edge of the image still curves slightly up in the middle. Any suggestions on methods other than a straight edge to determine if the screen is horizontally even?

Thanks in advance, I'll post some more pictures once I figure out a more forum friendly image host.
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post #7 of 9 Old 04-30-14, 11:47 AM
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Re: Help w DIY Sintra screen, multiple issues

Quote:
b18un wrote: View Post
Thanks Yainnis! Sorry for delayed response. The top edge of my image is 8" below the center line of my projectors lense, is this what the offset is? The wall is vertically level. I will try the rope trick when I get home tonight.
Yes, exactly!!

Can you tell us to which projector are you referring?
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post #8 of 9 Old 04-30-14, 12:00 PM Thread Starter
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Re: Help w DIY Sintra screen, multiple issues

Yainnis, I'm using an Optoma hd131xe. I spent several hours last night trying to align my screen to the projector and ended up worse off than I had been the day before I've been trying to avoid repositioning the projector mount since is a wall mount secured to concrete. When installing the mount I also managed to strip two of the screws and am not looking forward dealing with that. I have 14+' ceilings so the wall mount was my only real option. I plan on rigging up a stand and using the rope trick mentioned earlier to see just how far off I am before moving anything else.
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post #9 of 9 Old 05-01-14, 10:52 PM Thread Starter
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Re: Help w DIY Sintra screen, multiple issues

HI HT Shack,

Unfortunately I still have a 3/8"-5/8" gap at the top on the sides of my projected image I used the rope trick to determine where my PJ (Optoma hd131xe) needed to be and my original placement was off. So I sucked it up and re-positioned my wall mount (requiring more hammer drilling into concrete) and now when I throw the image onto the wall it's more square and in line with my optimal position. But when ever I hang the screen The bottom edge is wider (horizontally) than the top as far as I can tell using a level at each edge of the screen it's hanging d*mn near level (bubble is not crossing the lines). I've also noticed a lack of uniform focus (top will be sharp and bottom blurry) when trying to focus the image on my screen. I'm beginning to feel completely lost and would greatly appreciate and advice at this point
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