Easiest Way to Improve Picture Quality of Spandex Screen - AVS Forum
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post #1 of 7 Old 10-27-2013, 08:24 PM - Thread Starter
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I built this screen to use for rear projection from my garage to my side yard. The screen surface is a piece of a Spandex screen I bought from Ebay to experiment with outside. It works really well for rear projection and we've used it for front projection during rainy weather. With winter coming, outdoor viewing won't happen, so we will watch quite a bit in the garage (which is heated and cooled). The screen is a single piece of Spandex stapled to the back of the frame. It hangs of a wall in the garage for storage and that is where we watch it. Front projection isn't as sharp as rear projection seems to be. The wall is a medium to heavy texture and painted a "taupe" color. Would painting the wall a different color help with the picture quality? I'm using an Epson 705HD projector (2500 lumens, 3000:1). I can paint the wall any color (wife has approved this) because it is "my" garage. Any ideas would be appreciated.



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post #2 of 7 Old 10-27-2013, 08:41 PM
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painting the walls will certainly help... although not with sharpness of the picture quality.
for that you have to find a substrate you can line or back the spandex with... obviously one you can remove when weather permitting for outsoor rear projection.
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post #3 of 7 Old 10-27-2013, 08:53 PM - Thread Starter
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The material actually hangs against the wall. If I painted the area behind the screen (I have some Behr Silver screen left over), would that make a difference? Or should I get a piece of Spandex (color) and attach it to the back with Velcro to make it removable?
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post #4 of 7 Old 10-27-2013, 09:39 PM
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i understand that... however, unless the material itself is resting directly on the wall... then the wall would make no difference.

it's the light escaping through the spandex that creating your loss of PQ.
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post #5 of 7 Old 10-28-2013, 06:32 AM
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Quote:
Originally Posted by jwh92020 View Post

The material actually hangs against the wall. If I painted the area behind the screen (I have some Behr Silver screen left over), would that make a difference? Or should I get a piece of Spandex (color) and attach it to the back with Velcro to make it removable?

The use of a Light Gray Moleskin Spandex directly against the rear side of the Screen is one viable option....however if indeed the material lies directly against the wall, use that old standby SS is also very acceptable.

The telling issue left unaddressed...is in fact the Spandex "Touching" the wall. Loss of light through absorption being the cause of a loss of sharpness, that would indicate that the energy of the light that passes through is dissipated too much to be of any effect. Either distance from, or the color / absorbancy of the wall paint is the cause.

Unless you can "thicken" the material and reduce the total amount of absorption loss, things won't change enough to matter.

Some suggest Black as a backing, but all the same still applies. It would have to lie against the front surface's rear side, and be wholly impenetrable, or two things will happen.
  • Any light reaching the Black layer will be absorbed.
  • All light that passes through the top layer is simply wasted...gone.

Touching?
  • The presence of the Black will shift the color of the White Spandex toward a deeper shade of Gray than should a light Gray or Silver. That means attenuating light more severely.

I see considerable light below the screen, which is either "overspill" or light reflecting off the wall surface behind the screen. If the latter, then for certain the screen stands off the wall at least 1" or more. Taking your description at face value that doers not seem to be the case, so my final suggestion is to get a sheet of either Dark or Light Silver Moleskin Spandex and apply it loosely against the rear of the existing surface. Don't use Velcro, as it's bound to create at least some degree of stand-off. Rater use some flat, 1/4" x 2" wide Lattice and laying the second layer against the rear side and over the Trim, first attach the top edge across the length by using short screws through the Lattice / Spandex, then "lightly streching it across the bottom edge, screw it into place.

You only want to stretch it barely enough that is smooths out and does not produce any transfer of it's own texture against the front material.

To quote James T. Kirk;
"I'm laughing at the superior intellect"
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post #6 of 7 Old 10-28-2013, 01:19 PM - Thread Starter
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I just went out to take another look at the screen where it hangs. The Spandex does indeed touch the wall. As for the light below he screen, it is over spill. Unfortunately (from a theater standpoint), this is a working garage. I build cabinets for a living, so anything more than hanging this screen where it is (which was originally just a place to store it), plugging audio outs from the dvd player into my garage receiver and sitting the projector on a table when we watch out there is out of the question. Since I have the SS paint already, I think I'll try masking the area behind the screen, painting it and see what the picture looks like. If that doesn't help improve it, I'll get some silver Moleskin and see what that does What surprises me is that when I used this spandex for front projection outside (it was a 9' x 5' piece stretched really tight to almost 130" diagonal) the picture was actually really good. There was still a massive amount of light passing thru it, but it still looked good. Thanks for all your help. I'll try the paint later this week and post the results
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post #7 of 7 Old 10-28-2013, 01:33 PM
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Quote:
Originally Posted by jwh92020 View Post

I just went out to take another look at the screen where it hangs. The Spandex does indeed touch the wall. As for the light below he screen, it is over spill. Unfortunately (from a theater standpoint), this is a working garage. I build cabinets for a living, so anything more than hanging this screen where it is (which was originally just a place to store it), plugging audio outs from the dvd player into my garage receiver and sitting the projector on a table when we watch out there is out of the question. Since I have the SS paint already, I think I'll try masking the area behind the screen, painting it and see what the picture looks like. If that doesn't help improve it, I'll get some silver Moleskin and see what that does What surprises me is that when I used this spandex for front projection outside (it was a 9' x 5' piece stretched really tight to almost 130" diagonal) the picture was actually really good. There was still a massive amount of light passing thru it, but it still looked good. Thanks for all your help. I'll try the paint later this week and post the results

Considering the lumen output of your PJ, the issue may in fact be directly caused by having "too much" light returning off the rear wall surface. Certainly, it is true that excessive amounts of returning light can only be construed as being undesirable, and will result in both a lessening of contrast and reduction of sharp detail via "washing out".

White backing amounts to "light conservation". This can be imperative for those needing to use Spandex but who have PJs with under 1600 lumen output.

Gray or Silver backing relates to "light retention and contrast enhancement". PJs with great contrast and 2400 lumen can easily benefit from such a combination.

Black backing simply eats up all light lost through absorption, and/or prevents any bleed through of reflected light off rear surfaces. Once again, and PJ with sufficient lumen output need not worry about the lack of returning light.

So all that said, any darker, non reflective material behind your Spandex might make a measurable difference. c\Certainly SS applies, and might wind up justifying going darker still, since the Epson 705D doesn't have any real degree of exceptional Contrast going for it anyway....just a lot of brightness.

To quote James T. Kirk;
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