Color Mixing: By: Beyene Dumecha
Color Mixing: By: Beyene Dumecha
Color Mixing: By: Beyene Dumecha
• It is called additive because all of the wavelengths still reach our eyes.
Cont’d
• Red, Blue and Green are used as primaries to produce various colors by
additive mixing.
• The primary colors are independent- that the mixture of the two colors
will not produce the third primary color.
Red + Green = yellow
Green + Blue = cyan( blue-green)
Blue + Red = purple (magenta)
Red + Green + Blue = White
• These are the color obtained by emitted light
• Associated with television and computer displays
Methods of color mixing
(1) two or more lights are projected on the screen successively and rapidly
(2) Maxwell method- achieved by rotating color papers which cut precisely
into pieces of various sizes and mounted as segments on circular disk-
then additive color effect can be seen in proportion to the sizes of each
segment.
Subtractive color mixing
• is creating a new color by the removal of wavelengths from a light with
a broad spectrum of wavelengths.
The removal of part of incident energy can occur by the process of absorption and
scattering .
When the subtraction is made by absorption only ,it is called simple subtractive
mixing.
• The color of transparent materials like solutions and glass occur due to simple
subtraction of light energy by absorption.
• Yellow, Magenta and Cyan are the most commonly used primaries in subtractive color
mixing.
• The subtractive primaries are obtained by removing Blue, Green and Red lights from
white light.
• This can be achieved by using broad band filters known as substractive primary filters
White - Blue = Yellow
White _ Green = Magenta
White - Red = Cyan 9
Cont’d
• It is called subtractive mixing because when the paints mix, wavelengths are
deleted from what we see because each paint will absorb some wavelengths that
the other paint reflects, thus leaving us with a lesser number of wavelengths
remaining afterward.
A colored filter subtracts colors
by absorption.
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A colored filter subtracts certain colors
by absorption and transmits the rest
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A colored filter subtracts colors
by absorption.
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• When two subtractive filters are combined ,the primaries for additive color
mixing results.
• The addition of subtractive primaries will produce the additive color mixing
primaries of Red, Green and Blue. • Yellow + Cyan = Green
• Cyan + magenta = Blue
• Magenta + yellow = Red
• Yellow + Magenta + Cyan = Black
VISIBLE SPECTROSCOPY
Wavelength Range Absorbed Colour Absorbed Colour Seen By Eye
• When a sample only 380 - 430 Violet Yellow - Green
a) Source metameric: two objects do not match when source is changed (D65, A,C, CWF).
c) Observer metameric: when one observer says ‘match’ and another says ‘no match’.
d) Instrument metameric: when you get different colour co-ordinates from two different
instruments.
Cont’d
Metameric objects exhibit the
following:
As reflectance
curves are not
matched colours
are metameric
3) Substituting ‘working standards’ (made from the production formulation) for the original
metameric standard, whenever possible in the control and acceptance processes.
4) Correcting production colours without adding any ‘new’ (different) dyes to the product.
Reasons why colours do not match
• Colour is subjective: colour is a sensation, just like touch, and the colours you see are
purely subjective, as interpreted by your visual system and your brain.
• Lighting affects colour: the colour of an item will vary depending on the light, so it
will look different under incandescent light, fluorescent light, and daylight.
• Colours affect colours: your perception of colour will change, depending on the
colours around it, an effect called simultaneous contrast.
• Identical colours can be metameric: two colours are the same under one light but look
totally different under another light.
Cont’d
• Different observers perceive colour differently: colour is within us and colour
impressions are different for two different observers.
• The human eye is different: from spectrophotometer, camera, video display unit or
scanner.
• Different devices have different colour gamut: colour monitors (video display unit
of the PC) show colours that printers cannot print.