Our eyes can only detect a finite number of colors. These colors are defined by the sensitivity of the cones in our eyes. One institution that defined these sensitivities is the International Commission on Illumination (CIE). The CIE Standard Human Observer is shown in Figure 1.
Figure 1. CIE standard human observer. The plot shows the sensitivities of each rod on different wavelengths in the visible region.
From these sensitivities, a color gamut can be constructed to show all the possible colors that can a standard human can observe. Using the equations below we can calculate the boundary of colors that a standard human eye can observe.
P is the emittance spectra of the light source and X, Y, and Z is the sensitivity of the three cones of a standard human eye. Here we used a Dirac delta function centered at each wavelength in the visible region. This will represent a light source that has a single and unique color. Applying this method we'll get the color gamut of a standard human observer shown in Figure 2.
Figure 2. Color gamut of a standard human observer.
The objective in this article is to show how large is the color gamut of a certain display and how compare it to the color gamut of a standard human eye.
To construct a gamut of a certain display, we will need to get the emittance spectra of it while displaying a red, green and blue color. This will replace the Dirac delta function we used for the P. Then we plot the x and y then plot it with the color gamut of a standard human eye.
We used a Toshiba laptop LCD and a Epson projector for the displays. We made it display a red, green, blue, white and black color.
Figure 3. Color gamuts of a Toshiba laptop LCD and Epson projector.
We can see that the color gamuts of both the laptop LCD and projector is smaller compared to the color gamut of a standard human observer. Also we can see that when both the displays are made to show a black and white color, it is located at the region where red, green and blue are equal in magnitudes.
In summary of this article, we have showed the boundary of colors that a standard human eye can observe. Also, color gamuts of two displays are compared to the standard human observer.
Reference
- Dr. Soriano. Applied Physics 187 activity 5 manual.
- http://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html
- http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html
- http://en.wikipedia.org/wiki/Gamut
- Chromaticity. Wikipedia: The Free Encyclopedia. http://en.wikipedia.org/wiki/Chromaticity.
- International Commission on Illumination. http://en.wikipedia.org/wiki/International_Commission_on_Illumination.
- CIE FREE DOCUMENTS FOR DOWNLOAD. http://www.cie.co.at/main/freepubs.html.
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