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-   -   Homemade High-Gain Gray Screen (http://www.avsforum.com/forum/23-screens/19618-homemade-high-gain-gray-screen.html)

PapaSloth 04-02-2001 09:35 PM

Hi all, just a quick note about some experiments I did.

I have a relatively low lumen DLP projector (650 lumen, InFocus LP330). I've been using a light gray sheet (around elephant gray) and it's been working pretty well. But, while the gray helped give me richer blacks, I was losing a lot of detail in dark screens. So, I decided that a darker screen with higher gain would be perfect.

I noticed at a local Home Despot that they sell aluminized paint. It was over in the same section as the aluminum duct work/screens/etc., away from the "normal" paints. It's only around $8 per gallon, so it's pretty cheap. It seems to be a large amount of powdered aluminum suspended in an oil-based paint medium. I also picked up a gallon of flat black paint.

I was dumb and got a latex-based flat black which didn't mix well with the oil-based aluminum paint. But, a few squirts of liquid soap as a wetting agent solved that problem. I tried a few different darknesses on swatches, and got the best results with a medium-dark gray. This was around 3 parts black to 1 part aluminum, around the color of pencil lead when wet and around the color of dull solder when dry. The aluminized paint in the mix really picks up the light and increases the gain of the screen without too much shine. I'm quite happy with the results (except that my painting skills suck and it was really hard for me to get a relatively smooth, even coat).

I'm tweaking the frame a little bit, but I'll post some pictures when I have it back up.

Give it a shot, paint's cheap!

ssj2 04-09-2001 06:44 PM

Hey PapaSloth, I just did a search of this forum for gray/gain and found your post. Did you ever end up getting any pictures of your final product? I'm interested in building my own 92" wide 16:9 screen for use with my ceiling mounted 500 ANSI lumens LCD projector and would be interested in any tips. Thanks.

kelliot 04-09-2001 07:50 PM

I tried some of the Ralph Lauren candlelight silver but could never get it uniform enough.

------------------
Ken Elliott

RonF 04-11-2001 10:03 PM

I'm at some point going to try the gray paint process, Ken. Is it best to stick with flat finish, I'm guessing? Had posted a couple of places asking if there was any merit to mixing small amounts of the same color semi gloss with the bulk in flat, but no one ever responded.

------------------
Ron

Jay C 04-12-2001 11:03 AM

________________________________________________
Ken. Is it best to stick with flat finish, I'm guessing?
Had posted a couple of places asking if there was any merit
to mixing small amounts of the same color semi gloss with
the bulk in flat, but no one ever responded.
________________________________________________

Ron,

Yes, flat paint is very forgiving of poor painting skills http://www.avsforum.com/ubb/smile.gif and less than flat surfaces (your typical living room wall for example). As for mixing the paints of equal color with different sheens, what are you trying to accomplish? Increasing the gain incrementally? If so, why not buy the middle sheen and use a thinner (there is a latex thinner other than water that they sell at Sherwin-Williams that painters use to thin the paint before shooting it through an airless sprayer). If you need more gain (ie increased radiosity) using a glaze or other such additive or topcoat.

I personally used flat directly on my wall and have no complaints. The best part is that the image is the same brightness even at extreme angles (>60 degrees off center) which works out for my room geometry.

Jay

[This message has been edited by Jay C (edited 04-12-2001).]

kelliot 04-12-2001 10:06 PM

I saw it, considered it, but haven't tried it.

You can always try to "iron out" the wrinkles. Sorry, I couldn't help it.

The problem with aluminized materials is that they are very sensitive to non-uniformity. Stewart makes a very good aluminized material with a gain of 4.0 for 3D viewing. I have a sample and its very sensitive to any change in curvature.


[This message has been edited by kelliot (edited 04-13-2001).]

kelliot 04-12-2001 10:46 PM

The one thing that you may notice is taht even with relatively light grays (80-90%), the colors become much more saturated with gray material.

It helps to have a brighter projector. If the rated brightness at the screen is above 20 ft-L than the whites should be bright enough. If you have more than 30 ft-L on a white screen use an 80% gray screen, at 40 ft-Lamberts on a white screen use 60%, etc.

------------------
Ken Elliott

NickB 04-13-2001 01:26 PM

Frank,

When you tried both the aluminized and grey material did you re-calibrate using Avia or VE to set the correct contrast/brighness values? I am interested in the answer to this and would also like to know what store you found the white/grey blackout fabric at (I'm in the bay area also).

Thanks,
NickB

adnix 04-14-2001 10:02 AM

Quote:
<font face="Verdana, Arial" size="2">Originally posted by Frank M:
So I went back to the fabric store and got 3 yards of “ironing board materal†with an aluminized finish which came in a 54†width. . The cost was about the same as the light blocking material. This material is amazing. The whites are at least as bright and I swear that they are somewhat brighter. The blacks are definitely darker as well. The downside is that this material has a gain and any wrinkles are very obvious. It will require a very flat tensioned surface. Has anyone else tried this material?</font>
Sounds very promising! I've seen ironing board material that has a silver sparkly look: is that what you're speaking of? Do you notice it being sparkly while projecting?

Off topic: does anyone know if an online material store in the UK? Unfortunately there are no real material stores around where I live.



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