The Context - Artificial Human Sensors: Science and Applications - page 43

is made-up of sensing units, as mentioned earlier, called rods and cones. The
rods, located in the peripheral retina, provide us with our night vision, but cannot
distinguish color. Cones, located in the center of the retina, are on the other hand
not effective at night, but sensitive in perceiving colours during daylight condi-
tions.
The colour sensing cones each contain a light sensitive pigment, which is sen-
sitive over the visual range of wavelength. Our genes contain the coding instruc-
tions for these pigments, and if wrong coding instructions are structured, then the
wrong pigments will be produced, resulting in the fact that the cones will be sen-
sitive to different wavelengths of light. This process then may result in a visual
acuity. The colours that we perceive are completely dependent on the sensitivity
ranges of the genetic instructions for those pigments, and if not correct then the
visual sensations may result in a colour deficiency. There are many different types
and degrees of colorblindness - or more correctly called colour vision deficiencies.
This means that colour deficiency normally implies that some colour sensation is
absent and the person in some cases may not be aware of the deficiency.
People with normal set of cones and light sensitive pigment are able to see all
the different basic colours and their nuances combinations by using cones that are
sensitive to one of three wavelengths of light - red, green, and blue. Figure 2.6

shows the “normal” colour scale standardisation.

Figure 2.6. The standardised scale of a “normal” colour distribution.