Finished my DIY curved screen set-up with pics - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 83 Old 11-19-2007, 07:30 AM - Thread Starter
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I don't know of any other way to determine how much curvature is needed to correct for the pincushion effect other than to have the projector and anamorphic lens in place, then you do your correction on your actual set-up. The screen material that I used is a Vutec Brite White with a 1.3 gain and yes it does have enough body strengh and stiffness to maintain a smooth curvature when installed with the 1" Velcro border to the inside border of the frame.
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post #32 of 83 Old 11-19-2007, 08:40 AM
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Looks great, congratulations on your hard work, and the payoff. I have a similar plan in mind, finally got my cave plans approved by the city, need to do framing etc., many months away from seeing an image - sniff - oh well, have a couple flat panels in the house to "tide me over" until then.
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post #33 of 83 Old 11-20-2007, 01:20 PM
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Quote:
Originally Posted by tr6 View Post

The screen material that I used is a Vutec Brite White with a 1.3 gain and yes it does have enough body strengh and stiffness to maintain a smooth curvature when installed with the 1" Velcro border to the inside border of the frame.


Is there a noticeable difference among the various screen materials? I bought some Pfifer 4500 for a 10' wide DIY curved screen. Has anyone used this to make a screen? How would you suggest attaching the fabric to a curved screen made similar to TR6's screen? The velcro seems like a good choice, but I am wondering if there are any other ways. I would hate to use up the fabric only to find that there are sags in the screen.
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post #34 of 83 Old 11-20-2007, 03:28 PM
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I have phifer 4500 and might use the velcro, if your just sticking it on you have to get the kind with the acrylic industrial strength glue I believe. tr6 (different material) and one other person who also had 4500 had the velcro sewn on. My other option is to use window screen supplies. In Home Depot and lowes they have tracks you can attach to metal or wood, you'll have two channels with which to feed the spline to secure the material. Still a ways off tough.
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post #35 of 83 Old 11-21-2007, 02:50 PM - Thread Starter
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I recommend sewing the Velcro to the screen, this is the second screen that I have made with the Velcro sewn on and have had no problems, you can pull it pretty tight and it stays in place.
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post #36 of 83 Old 11-25-2007, 03:07 PM
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What did you use to cut the curved shape on the 2x4?
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post #37 of 83 Old 11-25-2007, 07:01 PM - Thread Starter
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I used a jig saw to cut the curve and then I smoothed it out with a belt sander. BTW it was a 2 by 6.
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post #38 of 83 Old 11-25-2007, 07:13 PM
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Very cool to say the least!
What screen did you use before this new one?

Drew
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post #39 of 83 Old 11-26-2007, 07:40 AM
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Quote:
Originally Posted by tr6 View Post

I don't know of any other way to determine how much curvature is needed to correct for the pincushion effect... The screen material that I used is a Vutec Brite White with a 1.3 gain and yes it does have enough body strengh and stiffness to maintain a smooth curvature

Thanks for that.

I understand the technique for identifying & correcting for "edge focus" and apparently the closer the screen the less-well a pj's optics correct for a screen being flat, but...

Since PJs are designed & sold for flat screens, is it reasonable for me to assume that if my pj-to-screen distance is sorta in the middle of the recommended range for a pj, that "pincushion effect" is negligible? If anyone here knows/has heard of any "rules of thumb" in this regard by all means speak up. WAGs are welcome too!
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post #40 of 83 Old 11-26-2007, 12:42 PM
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I am fairly sure the pincushion being discussed here is the extra effect from using the prisms for horizontal expansion. This is above and beyond the pincushion already corrected for by the projector's lens.
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post #41 of 83 Old 11-26-2007, 04:14 PM
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Quote:
Originally Posted by Riblet View Post

I am fairly sure the pincushion being discussed here is the extra effect from using the prisms for horizontal expansion. This is above and beyond the pincushion already corrected for by the projector's lens.

Oops, well duh! Does everybody concur? I figgered pincushion was anywhere, wasn't thinking in terms of the panamorph add-on.
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post #42 of 83 Old 11-27-2007, 11:15 AM
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If the lens does add some picushion affect and we curve our screen to account for it,then what happens when we passthru or remove the lens?

"Unless you continually work, evolve and innovate, you'll learn a quick and painful lesson from someone who has"
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post #43 of 83 Old 11-27-2007, 11:22 AM
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I think as has now been discussed in the CIH forum, there will be some negative impact as a pj's lens is designed to work with a flat screen. HOW negative will depend on the pj and throw/zoom etc.
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post #44 of 83 Old 11-27-2007, 11:41 AM
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Since the greatest distance-from-flat will be at the 2.35:1 setting, there will be less focal distance change for the 1.85:1 setting. In other words, the negative effect without the prisms on 1.85:1 material is less than the positives of 2.35:1 with prisms.
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post #45 of 83 Old 12-09-2007, 01:16 AM
 
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I authored a spreadsheet for calculating pincushion distortion, screen curvature, throw ratio and lots of other useful stuff based on screen height and throw distance only (that's actually all you need to know, plus an understanding of optics - which is my job).

If anyone wants to try it out, PM me. PLEASE INCLUDE YOUR EMAIL ADDRESS IN THE PM.

CAVX's broomstick is a good practical method, but the spreadsheet approach allows you to simulate your installation before deciding on a room size, projector model or where you're gonna buy the broomstick. Plug in your room ideas and play.
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post #46 of 83 Old 12-09-2007, 07:26 AM
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Quote:
Originally Posted by Aussie Bob View Post

I authored a spreadsheet for calculating pincushion distortion, screen curvature, throw ratio and lots of other useful stuff based on screen height and throw distance only (that's actually all you need to know, plus an understanding of optics - which is my job).

If anyone wants to try it out, PM me.

CAVX's broomstick is a good practical method, but the spreadsheet approach allows you to simulate your installation before deciding on a room size, projector model or where you're gonna buy the broomstick. Plug in your room ideas and play.

Bob, you got pm!
TIA!
____
Axel

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post #47 of 83 Old 12-09-2007, 10:20 AM
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Quote:
Originally Posted by Aussie Bob View Post

I authored a spreadsheet for calculating pincushion distortion, screen curvature, throw ratio and lots of other useful stuff based on screen height and throw distance only (that's actually all you need to know, plus an understanding of optics - which is my job).

If anyone wants to try it out, PM me.

CAVX's broomstick is a good practical method, but the spreadsheet approach allows you to simulate your installation before deciding on a room size, projector model or where you're gonna buy the broomstick. Plug in your room ideas and play.

Now where talk'n. Thanks for the post, PM sent
Gary

"Unless you continually work, evolve and innovate, you'll learn a quick and painful lesson from someone who has"
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post #48 of 83 Old 12-13-2007, 09:19 AM
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PM sent.

Have to say too, I love the OPs frame. Great work, I think I'll steal the idea.
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post #49 of 83 Old 12-18-2007, 11:36 AM
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Quote:
Originally Posted by Aussie Bob View Post

I authored a spreadsheet for calculating pincushion distortion, screen curvature, throw ratio and lots of other useful stuff based on screen height and throw distance only (that's actually all you need to know, plus an understanding of optics - which is my job).

CAVX's broomstick is a good practical method, but the spreadsheet approach allows you to simulate your installation before deciding on a room size, projector model or where you're gonna buy the broomstick. Plug in your room ideas and play.

Really? That's cool. I thought you'd need to know the specific characteristics of the HE lens being used. Can't a higher quality lens produce less pincushioning than a lower quality one?

~~~~~~~~~~~~~~~~~
My Basement Build Thread - House sold... no more theater :(
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post #50 of 83 Old 01-06-2008, 06:59 PM
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Hello Everyone,
room where I am going to put a I am newx to the site and need some assistance.
I have a 132" Curved Screen. I am looking for the way to figure out the arch. I read on one site that I should be 6" from center point, but am looking for a formula or a way to confirm that. Any help would be appreciated.
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post #51 of 83 Old 01-07-2008, 05:37 AM
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Send a PM to Aussie Bob in post number 45 for a spreadsheet to figure out your curve.
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post #52 of 83 Old 01-12-2008, 02:20 PM
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George,

After having priced pre-made curved screens, your technique is sounding very appealing, even if I have to pay a woodworker to cut the curve in the 2x6.

I've read your explanation of how you marked the curve on the 2x6, but I can't see how what you did produced a curved line. Can you please give a more detailed explanation for those of us who got D's in geometry.

Thanks.

MIKE

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post #53 of 83 Old 01-13-2008, 05:55 PM - Thread Starter
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Hello Mike, After cutting the 2x6 to the correct length I drew a line 1.5" from the bottom of the 2x6 across the whole length of the board ( it was about 10 feet long), This is the starting point or center bottom of the curve, and I left that much room for strengh. Now go to one end of the 2x6 and measure up 3.5" (that is how much curve my screen has) from the line I drew and hammer a long nail about halve way (put the nail about 1" from the edge) and do the same thing on the other end (the nails will be 5" total from the bottom of the board). Now go to the center of the board and depending on how thick the board that you will use to draw the line is ( mine was 1/4") hammer another long nail halve way thru 1/4" up from your starting line in the center (2.3/4 from the bottom). Now take the board that you are using to draw the curve and put the center of it under the center nail and pull the other two ends up and over the top of the nails at each end and there is your curve. Now you simply use a marker to outline the curve.
Hope that helps, George
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post #54 of 83 Old 01-14-2008, 09:16 AM
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Thank you, George. That explains it so even I can understand it.

When setting up the proportions for your screen did you use as your horizontal measurement the width along the curved line or the flat width? It probably doesn't make all that much difference, but since I'm doing it myself I may as well try to get it correct.

The screen I'm thinking of making is a bit wider than yours and I'm thinking of maybe using a 2x8 to give me a bit more strength where the curve goes deepest. My biggest problem may be finding a piece of lumber without warps or twists. I doubt I'll be able to find of piece of poplar or oak in that size locally and the softwoods I see in the lumberyards seldom are straight at anything over 8'.

MIKE

For every complex problem, there is a solution that is simple, neat, and wrong.
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post #55 of 83 Old 01-14-2008, 11:04 AM
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Quote:
Originally Posted by tr6 View Post

A few more pics I could not fit, The screen shots don't do it justice, it looks alot better in person,
George

Man this is a great setup. I didn't think making a curved screen could be this easy. I will have to give this a try.

My setup will have a short throw also, so I'll need a curved screen.
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post #56 of 83 Old 01-15-2008, 05:56 PM - Thread Starter
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Hello Mike, I made the measurements on the width before I cut the curve, so to answer your question it would be on the flat width. I also went thru a few 2x6's before I found 2 good ones. Don't worry too much about the finish if you are going to cover it with the black velvet. Also how much curve are you going to do? You might get away with 2x6"s instead of 2x8's.
George
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post #57 of 83 Old 01-15-2008, 07:36 PM
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Thanks, George. I may in fact go with a 2x6. I went to Lowe's this afternoon and the chances of finding a straight, unwarped 2x8x10 seemed dim. The 2x6's in 10' looked much better. Since I'm not sure of the final configeration of my room, I may just basically follow your pattern.

In your photos in looked like you nailed a 1x3 to the front of the curved cut. I can see how that would give good reinforcement but wonder if you left the 1x3 in place on the finished screen. It looks like it might create a shadow problem, but maybe it doesn't.

Given that the price I got for a pre-made curved AT screen was near $4K, I figure I'm way ahead even if it takes me a couple of tries to get it right. And as you point out, black velvet covers many sins.

MIKE

For every complex problem, there is a solution that is simple, neat, and wrong.
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post #58 of 83 Old 01-16-2008, 03:35 PM - Thread Starter
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Hello Mike, I'm not sure I understand your question but if you look at the pictures I have 4 1x3s across all four sides of the front . This is what gives you the 3" border, then I installed the screen material with Velcro on that border from the back (Velcro is sewn on the viewing surface side of the screen material). There is no shadow problem, the screen sits flat on that border.
George
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post #59 of 83 Old 01-16-2008, 05:30 PM
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George, that make a lot of sense. The back side of the 1x3 give a good place for the velcro.

MIKE

For every complex problem, there is a solution that is simple, neat, and wrong.
--H. L. Mencken
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post #60 of 83 Old 04-17-2008, 01:24 PM - Thread Starter
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I used a couple of L brackets mounted on the wall studs (the frame is pretty heavy) and placed the top 2x6 on the L brackets, that way I was able to move the frame left or right to center it. (a few private messages asked me how I mounted it) Hope that helps, George
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