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ChronoKing t1_iyhzdw2 wrote

Yes there is and it is important in a great many businesses. Hunterlabs is probably the largest business centered around color measurement (I know of). I recommend you click around their website.

In short, there are two main measurement methods, diffuse and spectral specular. Specular incorporates a surface's texture and will give different measurements for matte and glossy surfaces. Diffuse will specifically not include gloss effects.

For what the measurements are, they get translated into one of many, many colorspaces. A colorspace is just a way to define a color numerically. Often they are based on the limits of perception of the average human eye but not always. The ones I am most familiar with are Hunterlab's own L* a* b* space and CIE Yxy space. The "L*", "a*", "b*", "Y", "x", and "y" are the dimensions of the colorspace in much the same way as x, y, and z is in physics.

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h3rbi74 t1_iyi1d4g wrote

Wow you didn’t include a clickable link but I’m doing so now because that is a fascinating area of business I never would’ve spontaneously thought of! Gonna be clicking around here for a little while- thanks! https://www.hunterlab.com

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labroid t1_iyidtnz wrote

I believe you mean "specular" for "spectral" in the above.

Spectral measurements provide light intensity vs wavelength (or 'color') while specular measurements are of color including surface 'roughness'.

Beyond Hunter labs, a great read for beginner or experienced person is https://en.wikipedia.org/wiki/CIE_1931_color_space

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nerdybird t1_iyj1eqh wrote

Came here to link this. I am fairly certain that Hunter Labs only use the color space, it was defined by the International Commission on Illumination.

Nearly every major company that makes images or displays use this, such as Polaroid, Kodak, LG, and Foxconn to name a few.

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thickskull521 t1_iykp5ot wrote

Hijacking top comment to expand into the RGB part of OP's questions, and because I wanted to chime in that L*a*b* color space is also my favorite color space, because it is cartesian, square, and normalized: 1 unit in a certain direction is as equally perceivable (to human eyes) as 1 unit in another direction. Therefore, the difference in color between two objects (decmc) can be calculated using the Pythagorean theorem.

The "human perception" part is important. All these functions are defined based on how the human eye detects light, and how the human brain calculates color based on that information. The weighing functions can give similar solutions from different sources... For example, lemons and bananas look like the same color to us, but their absolute spectras are wildly different.

Now here's the thing. An RGB display is sortof backwards from how a human eye perceives color. They don't emit a nice spectrum... they emit little bands near defined red, green, and blue wavelengths. But, their emission bands stimulate human eyes good enough to spoof real colors. There are many different standards for RGB displays (they are optimized for different purposes, for example, fighter cockpits vs bright offices vs dark theatres) and this is why neat things like the blue-black-white-gold dress are possible.

I'm not aware of any publicly available tools to convert from spectra to RGB function; I'm building my own excel macros to do it right now. I don't think that's what you want though, unless it's super important to display it on a PC screen as realistically as possible, or you are building something that interacts with an RGB device. (Like a steampunk fighter jet helmet or VR headset lol.) For a web page, you cannot control how your customer's screen is color balanced so screw it. You would want to get the L*a*b* measurements if you wanted to do this for a QC purpose.

The most scientifically pure, objective way to analyze the optical properties of an object is variable angle spectroscopic ellipsometry (VASE). Especially for a reflective surface, because at sharper angles s and p polarized light will reflect differently. Ellipsometry data is then reverse engineered (using Maxwell's equations?) to build an optical model of the material. This is post-doc level physics and absolute overkill, but this is the purely objective way to define the optical properties of a material.

Edit: I found this. If you @ me I can model this up at work tomorrow and tell you if brass with different concentrations of copper will look different. I'm guessing they would, but the quality of the polishing would be the most important factor. https://refractiveindex.info/?shelf=other&book=Cu-Zn&page=Querry-Cu90Zn10

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pppollypocket t1_iykswqc wrote

I would say xrite is a big name in color measurement as well. They make a multi spectrophotometers that deal with reflective/refractive surfaces and are used in automotive for metallic paints, etc

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DiiJordan t1_iylhlcf wrote

Now I know where all the symbols come from. I work with ink and printing and we measure our colors but I wasn't trained to recognize the meaning of all that (which in all fairness, isn't necessary for the work I do with the inks).

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