Introduction Ingredients Spectra Attributes The Human Eye Color Mixing General Terms
Color Spaces How to measure Color Scales Color Effects After Images Contents

The Human Eye

HUMAN EYE on this page
on page 05.01
on page 05.02
COLOR-BLINDNESS on page 05.03






The retina is a complex tissue at the back of the eyeball containing light-sensitive cells and triggering nerve impulses via the optic nerve to the brain where the visual image is formed.
The light-sensitive cells are of two types, rods and cones. The rods for dark and white intensities and cones for colored light intensities. Rods predominate and are most sensitive to reduced light intensities. Cones are more prominent during the day as for color perception. The sensitivity of the rods is about 10.000 times as the cones.



1 = Iris The colored part of the eye located between the Lens and Cornea. It regulates the entrance of the light.
2 = Cornea The transparent, blood-free tissue covering the central front of the eye that initially refracts or bends light rays as light enters the eye. Contact lenses are fitted over the Cornea.
3 = Retina The innermost layer of the eye, a neurological tissue, which receives light rays focused on it by the Lens. This tissue contains receptor cells (Rods and Cones) that send electrical impulses to the brain via the optic nerve when the light rays are present.
4 = Rods The receptor cells which are sensitive to light and are located in the Retina of the eye. They are responsible for night vision, as non-color vision in low level light.
5 = Cones The receptor cells which are sensitive to light and are located in the Retina of the eye. They are responsible for color vision.
6 = Lens The eye's natural Lens. Transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the Retina.
7 = Pupil The opening at the center of the Iris of the eye. It contracts in a high level of light and when the eye is focused on a distant object.

The trichromatic theory of color vision are the three types of color receptors in the human eye. The actual existence of such receptor cells, known as cones,
have maximum sensitivities in the red, green, and  blue regions of the spectrum, with absorption peaks near 565 nm for red, 535 nm for green and 445 nm for blue. 


RGB-cones for the RED-GREEN-BLUE sensitivity 
also called as the SML-cones for Short, Medium and Long wavelengths. 


The RED sensitivity for the R-cones
or the L-cones

Range from 410 to 690 nm
Peak  580 nm

Peak range from 558 to 580 nm


The GREEN sensitivity for the G-cones
or the M-cones

Range from 440 to 670 nm
Peak  540 nm

Peak range from 534 to 540 nm


The BLUE sensitivity for the B-cones
or the S-cones

Range from 400 to 540 nm
Peak  440 nm

Peak range from 420 to 440 nm


When the human eye looks at a colored object and a few minutes later at a similar, it cannot tell us from memory whether the colors are different unless the difference is substantial.


The human eye does not function as an instrument for spectral analysis, that means, that the same color sensation can be produced by different physical stimulus. 


Thus a mixture of red and green light of the proper intensities appears exactly the same as spectral yellow, although it does not contain light of the wavelengths corresponding to yellow.  

The eye-brain mechanism of the human is incredibly sensitive. The human eye can differentiate about 10 million colors, but only by making a side-by-side comparison.
The human eye can only identify about 300 different colors from memory.


Any color sensation can be duplicated by mixing varying quantities of red, green and blue light. These colors, therefore, are known as "the additive primary colors".


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