


Colors of the Rainbow
Color Vision
Color Properties / Terminology
Color Luminance
The Color Wheel
Color Space and Gamut




Multi Model Color Blender
Color Converter
HSL Color Schemer
Colors by Name
1-2-3 Image Resizer
Black & White Picture Converter
Sepia Tone Picture Converter
Gray Card


Color Vision

The process of color vision unveils several interesting facts about color and our perception. For one that perceived brightness (luminance) is the predominant visual information we rely on for orientation and to identify objects. We also learn why all individuals perceive color a little different, or no color at all. Furthermore we get hints that might explain why certain techniques of combining colors in compositions have certain effects.
Light is the Origin



Color perception is a result of achromatic and
chromatic signals derived from light stimuli.
Chromatic signals (~ hue) are mostly derived from the
light's wavelength.
Achromatic signals
Light Stimulates Our Photoreceptor Cells

The eye has photoreceptor cells, called cones, which
we divide into three types.
S-Cones are
sensitive to
Each type of cone is less or more stimulated by
a light beam and passes on its stimulus value.
The next step is to transform these values into
values of three opponent-colors systems. The
luma system
(~ range from black to white, or
dark to fully illuminated respectively), the
blue/yellow system and the red/green system.
Finally the values of the three opponent-colors
systems are put together and make up our
color perception. Of course, we absorb multiple
light beams at once from different angles and
therefore can form an image of a scene.
The grayscale images on the right show how
much visual information is
contained in
each channel.
Cone Sensitivity



An interesting aspect of cones is their different
sensitivity in regards to wavelength. The
exemplary illustration on the right shows the
sensitivity curves for each type of cone.
We see that cones react to a wide range of wavelength
and how their curves overlap. We can also see that
sensitivity-peaks are not evenly spaced.
This demonstrates that for most wavelengths we need
the input of all three types of cones to distinguish
changes in wavelength and/or intensity (number of photons).
Furthermore, the illustration provides evidence that
the medium- and long-wavelength cones contribute the
most to our brightness perception, if we consider the
formula of the luma system from the above: L = B + (R + G).
Individual Color Perception

The physiological prerequisites for color vision allow
drawing the conclusion that there is no
uniformity in color perception among
individuals. Several physiological deviations
can cause a shift in color perception.
For individuals with "normal" vision these
shifts can be hardly measured. Less fortunate
individuals suffer from significant shifts
in color perception, called color vision
deficiency or "color blindness". Most of the
times this is caused by cones which are defect,
absent, or altered in their spectral
sensitivity.

