The Visible Spectrum
And how we see it
What is Visible Light?
• The cones in the eye are only sensitive to a
narrow range of EM frequencies.
• Visible Light – that which can be detected by
the eye
Red Light
780 nm – 620 nm
Orange Light
620 nm – 597 nm
Yellow Light
597 nm – 577 nm
Green Light
577 nm – 492 nm
Blue Light
492 nm – 455 nm
Violet Light
455 – 390 nm
Cones are the color-sensing cells of the retina.
• When light of a given wavelength enters the eye and strikes
the cones of the retina, a chemical reaction is activated
resulting in an electrical impulse being sent along nerves to
the brain.
Cones and Color
• The eye consists of three cones
– Red Cones
– Green Cones
– Blue Cones
• Each cone is sensitive to a different range of
frequencies of the visible spectrum
The red cone is not only activated by wavelengths of red light, but also
by wavelengths of orange light, yellow light and even green light.
The green cone is most sensitive to wavelengths of light associated
with the color green. Yet the green cone can also be activated by
wavelengths of light associated with the colors yellow and blue
Color by Reflection (Subtractive)
Certain wavelengths can be subtracted from the full spectrum (by being
absorbed by a substance) leaving the other wavelengths to pass into our eyes
All colors are absorbed
except yellow
White light – containing all
colors of the spectrum
hits an object
only the yellow light
waves are reflected
off the object and hit
the eye
*Most common way we see color*
Why do printers use
Cyan, Magenta and Yellow?
• A dot of G would subtract B
and R (two colors)
• Since Cyan is a combination
of G and B, it will only
subtract R (only one color)
• This leaves more colors to
reflect and mix together to
form all the colors we see
printed
Additive Color
Involves light emitted directly from a source into our eyes.
Combination of colors produces different colors
Where you see this process:
•Stage Lighting (projection lighting)
•Computer Monitors
•TV sets
White vs. Black
• White Light
– presence of all color
frequencies in the
spectrum
• Black
– Absence of all color
frequencies in the
spectrum