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Discussion Starter #1
I don't know much about mixing paints. That being said here is my question:

Why can't you just go to a paint store and tell them "I want a neutral gray with a RGB value of 185, 185, 185" ? I use 185 as a reference because I believe that is the value of my photography gray card used for white balance calibrating.

Does paint not mix on an RGB value scale?
 

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The short and simple answer is no because in the paint store they don't talk RGB color values and won't know what you are talking about. They can match a sample, or if they are a more reputable or skilled paint shop they can color match just about any brand of paint based on the color name and or number if you have that for them.

For example you can have them match your gray scale card, although as a straight off the shelf paint option that is going to be a bit too dark.

You certainly can get away with a simple OTS (Off The Shelf) gray and get an excellent image. In fact many have argued with me that a simple gray paint, as long as it is neutral and in a matte finish cannot perform as well as a complex mix, and I contend that in most situations that is rubbish!

The Valspar Signature Series paint comes in a very nice matte finish, and Lowes can mix up any color from any paint manufacturer we have thrown at them!

So the bigger question is what shade of gray you need! ;)
 

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Hi Mike,

As Bill stated, paint stores (at least none I have tried) can make a paint directly from RGB numbers. In theory it should be possible, but that is not how their color-matching software works. There is a great amount of data that gets used by that software that could be reported, but the software manufacturer (usually X-rite) just gives the info that they think the store needs to mix the paint and nothing more. I'll have to admit it's a bit frustrating at times for us. Sometimes at Lowe's I will remember to ask what the "Delta E" (the color difference between the color you are having matched and what the computer says it will make) is of the match when I have a color matched by them; about half the time the person mixing the paint doesn't even know that info is on the screen.

About your photographic gray card; if you mean a Kodak Gray Card for use with light meters, they are 18% reflective and are an N5 gray value in the Munsell Color System. The RGB is 119, 119, 119.

The RGB values of 185 would actually be a N7.5 value. Of course, your card could actually be this value if it is just for use as a white balance reference (the WhiBal card comes to mind). With todays digital cameras and light meters I guess there isn't much call for the old Kodak Gray Cards any more.
 

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Discussion Starter #4
Wow, thank you both.

Harpmaker: Should I be going down this road? Is a reference gray card (either 13% or 18% standard) what I should be thinking about when deciding a gray screen color? Are N-values that low unsuitable for a room with white ceilings and medium colored walls with no windows (will be blacked out). I will upload a picture soon for reference. Does N8, N9 work for most?

The projector I am leaning towards is the Optoma HD20. I was considering the Epson 6500UB but at 3x the price it doesn't seem to perform 3x as well from what I have read (I can't find stores in the area that have both for viewing)
 

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Depending on the screen size you want to make, the HD20 is a fairly bright PJ and can use a relatively dark gray screen. That said, I think a N5 or darker screen would be too dark for most people and screen sizes.

Off-hand, I think I would recommend Black Widow to you (a N7.5 mix that has white levels that look like a N8 or brighter screen was being used), but tell us what size screen you are thinking of using and we can give a better estimate. A photo would be great. :T
 
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