OTS Neutral Gray Universal Tint Codes and Known Finishes

exipnos said:

For the white paint have you tested the Liquitex titanium white? I'm in France and have problems sourcing the Glidden professional (or Delux professional). I've sourced the Liquitex and it seems much whiter then any of my other alternatives.

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Are you referring to the Liquitex BASICS line of paints? These are listed by Liquitex as being a satin finish and they will hot spot if used as a screen mix. The more expensive line of Liquitex Heavy Body Professional Acrylics have even more gloss.

I have not found the artist acrylic Titanium White paints to be significantly whiter than the bright white latex house paints here in the U.S., but I can't speak for your paints in France. If you would like to send samples (about 2 cm square) of any paints you want tested for color or brightness just PM Mech or myself and we will send you our address. Such samples can simply be mailed like a letter. We will test them with our spectrophotometers and usually report the findings to you the same day we get the sample.

exipnos said:

Yes its the basics line. I also have access to some other artist acrylic titanium or something called vivid white. I saw your previous note that Liquitex is to glossy so I have used the suggestion in the below thread to mix it with medium matte.

http://www.hometheatershack.com/for...esting/51685-titanium-sintra-development.html

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The idea behind mixing Liquitex Matte Medium with a paint, or paint mix, that hot spots by itself is to use the flattening agent in the Matte Medium to cut down on the gloss of the entire mix. This will work after a fashion, but the Matte Medium isn't totally clear so the more of it you add to your paint or mix the more it will drift toward yellow. Also the more Matte Medium that a mix contains the more translucent the mix will be and the greater the potential the mix will soften a projected image.

In your case where you are trying to get the whitest paint you can I would try adding some regular white water-based interior house paint to the BASICS Titanium Dioxide. It probably won't take much to decrease the gloss level so it won't hot spot.

How do I read the tests that you have done? I see the RGB values and the need for them to be close together for neutrality. What about the other numbers on the side? Does reflectivity mean gain?

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We use the CIELAB color space (also called L*a*b*) since it is one of the most respected and used ways of listing the color and lightness of a number of surfaces. The L* value can range from 100 (pure white) to 0 (pure black). The a* value denotes the amount of red or green in a color, positive values mean red and negative values mean green. The b* value denotes the amount of yellow and blue in a color, positive values mean yellow and negative values mean blue. The higher the value of a* or b* (no matter if it's positive or negative) the more intense the color is. In theory, both the a* and b* values should be 0.0 for a color to be a perfect neutral gray, but in the real world things just aren't that precise. Wbassett actually went back to school to learn about color science and in consultation with Dr. Mark D. Fairchild (a preeminent color scientist who recently completed 12 years as Director of the Munsell Color Science Laboratory) developed the neutrality standards we use for screens here at HTS. If both a* and b* are 0.5 or lower the color is neutral. If a* and b* are 1.0 to 0.5 the color is near-neutral. If a* and b* are 2.0 to 1.0 the color is acceptably neutral (meaning many projectors can compensate for the color "push" of the screen).

The N values we talk about frequently are the CIELAB L* values divided by 10. This value is used in the Munsell Color Space where it is called "V". The "N" is added when a color is considered to be a neutral gray thus it stands for "Neutral".

The RGB (more accurately the sRGB) color space data is added to our charts since that data can be entered into many paint programs so people can get an idea of what the color looks like. For reasons I won't go into here the RGB color space is not very accurate, but people want that data so we provide it.

The numbers on the side of the Spectral Reflectance Curve chart denote the percentage of reflectance of the individual wavelengths of light. My older spectrophotometer (an X-rite DTP-22) measured from 400 to 700 nanometers (by many considered the visible spectrum), but my newer X-rite i1 Pro spectro measures from 380 to 730 nanometers (a bit into the ultraviolet and infrared).

The color bar that runs along the bottom of the chart is reported to be a fairly accurate representation of the visual color response of the human eye at the individual wavelengths. You will notice that at frequencies greater than 690 nm and less than 420 nm the visual response is almost black, this is due to the poor perception of these wavelengths by the human eye.

Wavelength reflectivity is only one part of what is commonly known as "gain". The full term is "peak gain" because not only is screen color brightness or whiteness part of that screen attribute, but so is specular reflectance. The brighter or whiter a color is the more gain it will have, but also the more surface gloss a screen has the more gain it will have since more light is reflected back toward the viewer. The problem with gain resulting from surface gloss is that it will result in the screen hot spotting if it's too glossy.

The spectrophotometers that we use are designed to NOT see surface gloss and the reflectance values it reports are for what is called a Lambertian surface. This is a surface that has no gloss whatsoever and reflects light in all directions equally.

I 'd like to add the white base of Benjamin Moore in the list. The code is 515 01 White, flat finish of course...i call it ''Dove''!!

So I've been testing 3 different samples of neutral grays these last few days trying to narrow down my options. I've snapped a few pictures as well hoping that they may help someone else one day with this same kind of comparison.

The 3 colors I'm testing are "Grimmy's Grey" (N5.2), "Icon Grey" (N6.25) and "Granite Gray" (N6.7). The screen itself is around an N8.0 I believe? It is "Carl's FlexGray" screen material.

In the photos the smaller sample on the left is "Granite Gray", the upper portion of the large sample is "Icon Grey" and the lower portion is "Grimmy's Grey". Some photos are with lights on, most are with lights off.

I'm still torn between these 3 colors and cannot come to a decision. Each one looks pretty good, I feel the Grimmy's Grey may be a little too dark.

The screen is 80" and the projector is a BenQ W1070. I'm trying to cut down on the brightness of the picture, even with all the lights off the reflected light is lighting up the room pretty well.

Any advice is greatly appreciated

Album here:
http://imgur.com/a/lMQrh

Well, let's do some math...

80'' screen in 1,78:1 means 1,80 s.m.

Grimmys Grey's gain is about 0.25 (paint plus finish)
Icon Grey's gain is about 0.33 (paint plus finish)
Granite Gray's gain is about 0.35 (paint plus finish)

Benq on low lamp and cinema mode (without calibration) outputs around 850 lumens. So:

On GG you 'll have 10,97 FL, on IG 14,48 FL and on GG 15,36 FL.

Considering over time that the lamp will lose power, i would say Granite Gray or even a tad lighter would be the wiser choice.