Questions

 

 

QUESTIONS and CONSIDERATIONS:

Why are there different theories about color?

Why isn't there just one set of primary colors?

How are the two ways to mix color different?

What usually gives objects their color?

What happens to light when mixing colorants such as paints, dyes, and inks?

Which primaries are used when?

ANSWERS BELOW:

Why are there different theories about color?

It appears that color is as much a part of human vision as it is of the physics of light and matter. The study of color and light is still a part of scientific theory. Knowledge about how color works is constantly being adjusted and refined, even as you read this. However, enough practical knowledge about color is understood to enable its use in many ways. The information on this website includes some of these observations.

Why isn't there just one set of primary colors?

One way to look at it is that all color mixing needs light. Without light, we would see nothing at all.

The main reason for two sets of primary colors is the way the colors combine, and the way the eye sees the new color. Color is mixed from direct light one way, while reflected objects and filters mix color in another way.

RETURN

How are the two ways to mix color different?

1. First lets look at the color primaries of light.

RED GREEN BLUE:

 

With television and computer monitors, the three primary colors of red - green - blue make all other colors. Other colors are mixed from different amounts of brightness of these three colors. The colors of red - green - blue appear mixed because the three colors of dots on the screen are too small to be seen. Our eyes blur the dots together. If you look closely at a TV screen with a powerful magnifying glass, you will see only three color dots (or stripes, or rectangles).

red

green

blue

Monitor or television
screen magnified.

If we shine colored light bulbs on a white wall, we can see different colors formed where the light overlaps. The light is transparent. We can still see the light from each light bulb. The colors are added together when they shine on the same area.

Color is a property of light and matter, but it is also a part of human vision. We cannot separate the individual colors in a color mixture with our eyes. We see only a mixed color that is different from the original starting colors. So if we shine light of red color and light of blue color on a wall, we may see a completely different color called "magenta". Experience may help us to see magenta as a somewhat reddish color with some bluishness in it. Basically we will see magenta as a different color.


Red 

and 

Blue  

Magenta

when mixing light

    

When it pertains to light, yellow can be made by a mixture of green and red light

Red  

and  

Green  

=  

Yellow

when mixing light

 

Even when we look at a single yellow colored light bulb, we cannot see the green or red that makes it look yellow to us. Scientific devices can show that the illumination from a yellow colored tungten bulb still contains the red and green. It is the eye and brain that tells us the color is yellow.

Prism shows yellow light can also be a combination of red and green:

 

Green

Red

Yellow colored tungsten bulb Prism

So we can see that light mixtures of red - green - blue are needed by the human eye in order to see all other colors. Recent scientific data confirms this.

2. Now let us look at these next two questions about why cyan, magenta, and yellow paint, ink, and dye mix together in a different way than the light primaries of red, green, and blue.

 

CYAN MAGENTA YELLOW:

What usually gives objects their color?

The surfaces of objects, and the substance of clear objects affect the light that shines on them. The light may be absorbed, or it may be reflected by objects. The light may be absorbed, or transmitted by transparent objects such as colored glass.

SUN
LIGHT

 

A way to observe that light is being absorbed is to place a light colored object and a dark colored object in direct sunlight. For example, a light rock and a dark rock. After awhile, the darker rock will feel hotter than the lighter rock. Why? Sunlight is energy. More sunlight bounces off the light colored rock. More sunlight is absorbed by the dark colored rock. More of the energy from the sun is captured by the dark rock, so it feels warmer.

An object may both reflect some light, and absorb some light at the same time. If it reflects certain colors from white light, and absorbs other colors, the object will take on a color of its own.

Object Absorbs Reflects We see

blue  

green

red red

red 

blue

green green

red  

green

blue blue
red

blue  

green

cyan
green

red 

blue

magenta
blue

red  

green

yellow

What happens to light when colorants such as paints, inks, and dyes are mixed?

Paint changes the surface of objects. Mixing paint combines colors physically into one newly formed color. Only the light bouncing off the mixed paint is what we see. So red paint will absorb some light out of the light that shines in it. Green paint will also absorb some of the light that shines on it.

When red and green are mixed, the mixture captures all of the blue, and part of both the red and green from the reflected light.

Paint Absorbs Reflects MIXED
red

blue 

green

red
and
green

red 

blue

green
red + green mixed

red 

blue

green

red 

green

brown

All or most of the blue in white light is already absorbed (subtracted) by red and green paint. When red and green are mixed, some of the red and green is also absorbed (subtracted) from the light. This absorbed light will make the mixture look darker than the red paint, darker than the green paint. Usually a - dark brown - will result from such a paint mixture. Yet dark brown is actually a very dark yellowish orange. As a yellow light bulb is dimmed, it will begin to appear browner.

CONCLUSION:

So if it's mixtures of light that enter our eyes directly, we need the additive mixing system of red - green - blue for accurate color.

When light reflected off objects enters our eyes, then our eyes are still using the primary color system of red - green - blue . The eye works that way.
     
The second primary set of colors of cyan - magenta - yellow are used only to mix colors physically or by placing one color filter over another.
     

 

 

RETURN

WHICH PRIMARIES ARE USED WHEN?

Color light is mixed:

RED GREEN BLUE red
green
blue
  • When colored light bulbs or spotlights shine on the same area.
  • When our eyes combine the color dots of light on a television screen, or computer monitor.

Colors are mixed physically:

cyan CYAN MAGENTA YELLOW
magenta
yellow
  • When we mix paint together.
  • When clear color liquids are combined.
  • When we place one color glass in front of another.
  • When a printing press prints several color inks on top of each other on the same paper.
  • When several transparent color layers are used to make a photo, a slide, or movie film.

 

Click on other topics listed at left above or as listed in chart below 

Color Systems...

Introduction

Additive Color

Subtractive Color

Color Applied...   Color Vision Painting - Art
    Monitors- TV Photography
      Lithography
       
Other Items... Common Queries   For Kids: MIX IT SITE INDEX
  Translation      

Text, and all graphics, artwork, and photography
© 1997, 2007 by Robert Truscio (All rights reserved)

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