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This thread is for the investigation and discussion of Spandex fabrics when used to make DIY screens. The primary use of these fabrics is to make an Audio Transparent screen so that audio speakers can be placed behind the screen rather than around the screen as must be done when using an existing wall as a screen or using some other solid substrate as a screen.

A member here (maxmercy) was kind enough to send me some samples of Spandex to measure with my i1 Pro spectrophotometer. The results and commentary are below.

METHOD OF SAMPLING
To act like a screen I placed the Spandex samples over the sensor of my spectro and then pulled the fabric taut to get it flat over the sensor. There was minimal ambient lighting during the testing and further tests were done to prove that only the screen material was read by the spectro. This would equate to a screen consisting of a single layer of fabric that is taut, but not highly stretched. Such a screen would produce the brightest image that fabric is capable of since the more the fabric is stretched the larger the "holes" are in the screen.

The White Spandex Samples
All of the white Spandex samples are far from color neutral. Notice how they increase their reflectance drastically beginning in the blue-green portion of the spectrum.

The brightest of the samples is the Moleskin Matte white at N8.4, but the darkest, Milliskin Matte White, is not that far away at N8. What people will see as a brightness difference between these fabrics has as much to do with color differences as with brightness differences.

The Moleskin fabrics are made of 8 ounce material, the Milliskin is 6 ounce. The lighter weight the fabric is the more AT it will be.








The Gray Spandex Samples
The gray Spandex samples are neutral enough so they will chart on my chromaticity chart so that is included with the spectral reflectance chart.

Only the Rough Moleskin Silver sample is neutral enough to fit into our Acceptably Neutral parameters, but like the rest of the gray Spandex samples it has a large increase in reflectance in the red portion of the spectrum. What this means is that while these fabrics may appear fairly color neutral under D65 lighting (the white light standard, or white point, for the video industry), under warmer light sources (especially incandescent lighting) reds will be reflected approximately twice as much as other colors. This is called illuminant metameric failure.

All of these grays will make a rather dark screen. The brightest, Moleskin Matte Silver, is N6.8 and the darkest, Milliskin Light Silver, is N5.9.

The Moleskin fabrics are made of 8 ounce material, the Milliskin is 6 ounce. The lighter weight the fabric is the more AT it will be.






 

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Discussion Starter · #5 ·
Thanks for this, Harp!
Thank YOU for the samples! :T

What would be your recommendation for a non-light controlled room (minimal windows, but light colored paint)?

JSS
That depends on the size of the screen and the image brightness being output by the PJ. You would need some serious lumens to offset the darkness of the gray Spandex so most of the time I would probably suggest using the Matte White Milliskin.

More investigation will be done into Spandex screens. Some new info to report is that the Milliskin is ~.002" thick, the Moleskin ~.003" thick and the Rough Moleskin ~.004" thick. The thicker the material the less transparent it will be to sound.

Both of the Rough Moleskin samples have a surface that seems to sparkle which could cause a graininess in the projected image depending on how close the viewer is to the screen and how sensitive they are to such things.

As time and money permits I intend on making some sample Spandex screens and comparing them to painted screens.
 

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We generally don't allow links to AVS, but since you are the OP (original poster) and have a lot of data already posted there I'll pass this decision up the line to an administrator.

I'm not done. Have to do some more testing. And I have some XD here to test.

So is this spandex any good? Optically.
From what I can tell just from the small samples I was sent Spandex will work well as a screen, but they will be darker than many people think just from eyeballing the fabric. The "white" Spandex has a light reflectance of ~N8 depending on how hard it is stretched, the less the better.
 

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Oh, sorry, I didn't realize that would be a problem. I'd repost the data but its a WIP. Once I've measured some more material and experimented with distance and angle I could summarize it and repost it. Sorry again, I don't hang around here much as you can see. Just lurk a little so I don't know the rules :eek:
 

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We generally don't allow links to AVS, but since you are the OP (original poster) and have a lot of data already posted there I'll pass this decision up the line to an administrator.


From what I can tell just from the small samples I was sent Spandex will work well as a screen, but they will be darker than many people think just from eyeballing the fabric. The "white" Spandex has a light reflectance of ~N8 depending on how hard it is stretched, the less the better.

I noted this on my Spandex screen built. The White moleskin was as dark as my Unique Gray painted screen when I compared the two sides by sides, and measured 100IRE with the i1D3 meter.

I also noted some graininess on the spandex material compared to painted screen. The graininess is not quite apparerent on 1080p source, but you can definitely noticed it on 720p or streaming/OVA sources.

Also Tux's tests show that AT properties of these materials are pretty questionable.

I am in the process of either going back to my painted screen or pay extra cash for the XD material. The painted screen is sharper/clearer compared to Spandex.

Thanks for all the testings/data guys.
 

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Chris Seymour said the following to me in an e-mail:

"We are working on a material that is easier to use for DIY purposes and is a darker gray but I'm currently testing it and don't yet have results."

This is promising for DIY AT screens...for those without the best light control.

JSS
 

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Discussion Starter · #12 ·
Chris Seymour said the following to me in an e-mail:

"We are working on a material that is easier to use for DIY purposes and is a darker gray but I'm currently testing it and don't yet have results."

This is promising for DIY AT screens...for those without the best light control.

JSS
Yeah, Chris is a cool guy. It's a bit before my time, but I understand he started out building his own DIY AT screen and then put the knowledge he gained in his search into starting a business - that's the American dream.
 

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From a what I understand, it is a woven vinyl product originally used for shade cloth. He then got some manufactured for AT screen material, and still caters to DIY (where he came from) which is very nice.

JSS
 

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I have a link on the first page. I posted everything on AVS. I'll transport it here as well when I get a chance, but don't spend much time here. And writing it all up takes a bit of time, it needs context or it doesn't make sense. Sorry Max.
 

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Discussion Starter · #18 ·


Here is a Spectral Reflectance Chart of a combination of White Matte Milliskin Spandex over Light Silver (which, at ~N6, is actually a dark gray) Matte Milliskin that is being recommend for screen use on another forum. As can easily be seen by comparing this chart with the charts for the individual Spandex material charts, in the first post of this thread, light is being reflected from the Light Silver layer and illuminating the back of the White layer then continuing through the white layer to reach the spectrophotometers sensor (or the human eye in the case of screen use). This does two measurable things, first it produces a screen color that is a combination of the reflective qualities of the two fabrics and second it brightens the image a bit. The problem with this is the two fabrics each have unusual spectral curves that when added together (which is what you see in this chart) combine the color problems of each fabric rather than cancel them out. The white fabric has a steep boost in the deep blue section of the spectrum while the light silver has a steep boost in the red area. It is in question whether both can be compensated for at the same time through projector calibration, and the overiding question is why use the silver fabric as a secondary layer in the first place. The answer is YOU SHOULDN'T! The best Audio Transparent screen will result from using a single layer of the white fabric alone. The main problem with this is that almost any source of light (power lights from any equipment or any light reflected from objects) behind the screen will show through the screen material and appear as part of the image. A similar problem would occur if the wall in back of the screen was painted a light color. The obvious answer is to use a black second layer to absorb as much light as possible that makes it's way through the first layer or tries to come thought from behind the screen. This is why many commercial screens have a black rear layer of material as well. The only layer of the screen that we want reflecting light back to the viewer is the top of the first layer. This is true whether using a fabric or a painted screen.

So what does happen with a white/silver dual layer Spandex screen? It's simple physics folks; the light that passes through the white layer will be diffused like light that passes through a translucent white milk jug and will blur the image. That light will then strike the silver layer and some of it will be reflected back toward and through the white layer TO COMPETE WITH, NOT JOIN, with the light reflecting from the surface of the white layer. The result MUST be a softening of the projected image. The other thing that happens is that the light from the silver layer will brighten the perceived image a bit, but such brightening from a diffuse source MUST in fact LESSEN the contrast of the image not increase it as some misguided people suggest.

It's really amazing to read how those advocating a white/gray dual layer Spandex screen suggest how such a screen works. Their theories don't work when using a mirror as a background and they fail even more so by using a diffusive fabric as a rear reflective layer. Painted and fabric screens do not and can not work this way. You will notice that anyone saying they can will offer no objective proof of performance and, at best, try to prove their theories by showing screen photos that in fact prove nothing, one can't even tell from a "screenie" (a photo of a screen being used) if the screen in question is white or gray! The physics of light (refractive and reflective) are well known and have been proven over and over again as the scientific method demands. Those that ignore them base their theories on hot air and wishful thinking.
 

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Discussion Starter · #20 ·
Thanks for measuring Harp!


Too bad they don't pan out as well, the price was right for these fabrics...I'll wait for the grey offering from Seymour.

JSS
No problem. :T

We tend to cater to people that want the best "movie experience" possible in their home theaters here at HTS. For those situations where exact color reproduction isn't demanded, and the needed lumens are available, a Spandex screen made of the materials measured in this thread would probably work fine.
 
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