If we want retroreflectivity as well?? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 40 Old 12-25-08, 08:31 AM Thread Starter
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If we want retroreflectivity as well??

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Harpmaker wrote:
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custard wrote:
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mechman wrote:
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custard wrote:
i have been able to locate some glass bead paint for retroreflectivity.
it can be rollered but i suppose spraying is going to give the most uniform finish.
this type of screen should only be intended for the ones who want the brightest picture on axis i think


its 1.50am here so merry xmas and i'm gonna need to sleep now otherwise i will fall asleep while eating the turkey!
Interesting. I was looking at something last week that I was thinking would possibly result in something like this. That stuff is pretty expensive. The stuff I was looking at would cost around $30-40 or 20-30 pounds.

Golden glass bead gel and a matte acrylic varnish. Add that to Black Widow... just thinking out loud here.
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I've played around with the thought of using a retro-reflective base coat, but I think such a top coat would be too much. Also, the glass beads used would have to be VERY small; the size of the bead is what makes many screens look 'grainy'. Remember the old slide projector screens of yesteryear? I have not found a source for such small beads.

My idea was to have a translucent paint over the retro-reflective base coat.
yep, the possibilities are endless with what we can try...

they do say that the beads are microscopic on the site so hopefully they are small enough.
also it is water based so it should mix in with the current mixes.

120ml of the stuff is going to cost me about $30 (20) including postage.

i'm thinking along the lines that if we are not able to remove the bright flecks with AAA-M then it may be better to introduce it in to the AAA-F BW.
to make the AAA-F lighter we need to reduce its ratio.
a 6:1 AAA-F may get us to N8-N8.5.
whatever angular gain is lost by reducing the ratio could be replaced by the glass bead paint in a retroreflective manner.

if we can keep the amount of the glass bead paint to a minimum then cost issues are alleviated - you can buy as less as 30ml for $7 (5).

in the end if the user wants the the best option for themselves they may be willing to pay the extra amount - it will still cost alot less than the buying a commercial paint/screen with equivalent properties.

i think i will order some of the clear (120ml) and a smaller amount of the grey (60ml) for testing purposes.
It would certainly be interesting to see how that paint worked in a screen mix.

My idea was that either using a retro-reflective base coat, or perhaps with the beads in the screen mix itself, the paint surrounding the beads would diffuse the retro-reflectiveness a bit to provide more gain off-axis and less on-axis. When you stop to think about it, a true retro-reflective screen wouldn't work well with PJ's since the projector is almost always mounted above or below normal viewing level.
i see your point - we dont want something that is a perfect retrereflector only. hopefully the beads are not perfectly spherical so the light is diffused out somewhat. i would have thought the projector on the table will have more to gain than a projector placed under the ceiling in this situation.

the commercial high gain screens using glass beads get around this somehow
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post #2 of 40 Old 12-25-08, 10:19 AM
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Re: If we want retroreflectivity as well??

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i see your point - we dont want something that is a perfect retrereflector only. hopefully the beads are not perfectly spherical so the light is diffused out somewhat. i would have thought the projector on the table will have more to gain than a projector placed under the ceiling in this situation.
My guess is that the beads would be pretty round; I think the manufacturing process lets the surface tension of the molten glass form the sphere. How they make them microscopic is a complete mystery to me.

If a screen depends on retro-reflectiveness alone to create gain, then the closer the viewer is to the PJ projection axis the more gain they will see.

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the commercial high gain screens using glass beads get around this somehow
The only way around the problem I can see is to somehow diffuse the reflected image. How to do that is the $64 question.

Many beaded screens don't diffuse at all, or extremely little; the beads can actually be removed if the screen is cleaned (they come off).

To get maximum retro-reflectiveness, the glass beads are a surface treatment only - they are only half submerged in the top coat of finish/paint/glue. To make DIY reflective signs, the beads are placed in a paper cup that has a very small hole in the bottom; the cup is shaken over the sign and the beads fall onto the still-wet paint used to make the sign. Very much like powdering a doughnut with confectioners sugar.
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post #3 of 40 Old 12-26-08, 01:40 PM
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Re: If we want retroreflectivity as well??

I went to Michael's Crafts today and while they didn't have the Golden Glass Bead Gel, they did have Liquitex Glass Beads Texture Gel which I assume is similar. The glass beads in the Liquitex product are way too large for anything we want to do, IMO.
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post #4 of 40 Old 12-26-08, 08:04 PM Thread Starter
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Re: If we want retroreflectivity as well??

what would we consider the maximum size allowable?
and how large were the liquitex beads?

i take it we should be able to see them only slightly with the naked eye?
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post #5 of 40 Old 12-26-08, 10:22 PM
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Re: If we want retroreflectivity as well??

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what would we consider the maximum size allowable?
and how large were the liquitex beads?

i take it we should be able to see them only slightly with the naked eye?
I wish I could give a size range in millimeters or microns, but I can't. I also haven't found a stated size for the Golden or Liquitex beads, but the beads in the sample chit of the actual paint could be seen as separate dots from several feet away. They were also very visible in the jar where they made contact; it looked like small pearls of tapioca.

I'm guessing that the beads themselves, in the size we want, would look like very fine sugar, or perhaps even flour.

I'm getting a new USB microscope next week (found one on sale) so I might have some photos for you.
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post #6 of 40 Old 01-04-09, 04:18 PM Thread Starter
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Re: If we want retroreflectivity as well??

i received the samples of the retroreflective paint today.
so i did a quick test.

after shaking i dipped my finger into the mix and smeared a layer of each onto a piece of paper.

my first observation is that i can see some retroreflection aswell aswell as specular reflection. the grey mix seems more reflective than the clear mix.

i would explain the texture as similar to rubbing my finger over fine sandpaper with a grade 0f over 500.

i think the particles are smaller in the clear coat.

i will email the manufacturer to see if they can enlighten me on the actual size of the particles in the mix.

more to follow

i dont wether they are that small as the the link is showing but the are definitely difficult to detect with the naked eye on the clear coat.
here are some crude pictures i took. camera is set to colour in a dark room. the photos are taken at about 45 degrees with flash on. the particles should reflect back to the camera (flash) if they are retroreflecting. quarter dollar for scale.



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post #7 of 40 Old 01-05-09, 02:07 PM Thread Starter
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Re: If we want retroreflectivity as well??

thanks mech.

got the scope working.

heres the shots of the grey reflective paint

20x


200x


looks like there are other particles present aswell as glass beads.
the other particles are showing a prismatic coloring
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post #8 of 40 Old 01-05-09, 10:16 PM
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Re: If we want retroreflectivity as well??

I think the simple answer is that those beads were treated with an iridescent coating just like mica flakes are coated. What a horrible thing to do to those little innocent, defenseless glass beads.
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post #9 of 40 Old 01-06-09, 12:07 PM Thread Starter
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Re: If we want retroreflectivity as well??

the clear paint definitely has clear glass beads, but even with them in certain situations i can get the same effect.
so yes mech, i dont think there is a problem with the grey paint as much as i thought.
i'll be posting some samples for harpmaker to analyse.

testing has been quite interesting. i have been able to obtain some promising results.
here is a comparison to a white panel which was painted over with a mixture which included the clear paint.
on axis especially at the retroreflective angle i am seeing a dramatic increase in gain

first of all the spectro readings after 3 days of curing:

the white portion of the panel:
Lab 94.69 -0.51 1.52
RGB 240 240 237

the retroreflective paint on the white panel
Lab 93.74 -0.58 1.90
RGB 237 237 233

here are the results:

projector on low table top
black and white images
retroreflective paint on RHS

room lighting


angular reflective position just over height of panel


sitting position, on axis


20 degrees sitting


30 degrees


45 degrees


60 degrees


60 degrees LHS


grey scale sitting


grey scale zoom, sitting


the beads seem to be working very well, even in the angular postion

i am truly amazed!
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post #10 of 40 Old 01-06-09, 12:12 PM Thread Starter
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Re: If we want retroreflectivity as well??

tests with the projector just below ceiling were also carried out
throw distance 14 feet?
no zoom appllied on lens of hd65
sitting position very slightly (1 foot) in front of projector
the reflective paint is on the LHS this time
camera set to black and white except last photo.

retroreflective position - camera near projector


camera at middle of panels


sitting position


below sitting position - position of my knees


20 degrees sitting position


30 degrees sitting


45 degrees sitting


60 degrees RHS


60 degrees LHS


grey scale sitting - reflective light from the black and decker box is distorting lower bars somewhat


grey scale upper bars, sitting


color bars sittting



WHAT do you think guys????
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