Fundamental Principles of Color Reproduction

The three fundamental attributes of color are:Hue\Lightness\Saturation.

1. Hue

Hue, also known as color tone, is mainly determined by the dominant wavelength of light. It is the fundamental characteristic that defines the type of color perceived.

2. Lightness

Lightness refers to the visual perception of the brightness or darkness of a color. It depends on the amount of light energy reflected from an object into the human eye and the characteristics of human visual perception.

3. Saturation

Saturation, also known as chroma, refers to the purity and vividness of a color. A color with 100% saturation represents completely monochromatic light.

Additive Color Mixing (Color Light Addition)

The additive color mixing principle is based on the combination of different wavelengths of light.

The additive color relationships are:

R + G = Y (Yellow)

R + B = M (Magenta)

G + B = C (Cyan)

R + G + B = White

Two Characteristics of Additive Color Mixing:

① The brightness of the mixed light increases

After mixing, the brightness of the resulting light is equal to the sum of the brightness of the original light components. This is because the total light energy increases during the mixing process.

② The saturation of the mixed color decreases

The saturation of the mixed color is lower than that of the original color components. Therefore, additive color mixing cannot produce a color with higher saturation than the primary colors.

Applications:

The additive color mixing principle is widely used in:

Color television displays

Projection systems

Electronic display technologies

Subtractive Color Mixing (Colorant Subtraction)

The subtractive color mixing principle is based on the selective absorption of light by colorants.

The subtractive color relationships are:

C + M = B (Blue)

C + Y = G (Green)

M + Y = R (Red)

C + M + Y = Black

Characteristics of Subtractive Color Mixing:The major difference between subtractive color mixing and additive color mixing is that:During subtractive mixing, the reflected or transmitted light energy decreases because colorants absorb certain wavelengths of light. Therefore, the more colors are mixed, the darker the resulting color becomes.

Applications:

The subtractive color mixing principle is mainly applied in:

Color printing

Painting

Photography

Color Separation

Color separation is based on the principle of subtractive color mixing.

Using red, green, and blue optical filters, a color original is separated through photographic exposure or scanning to obtain three separation images representing the original image information:Cyan separation\Magenta separation\Yellow separation.

Photographic Color Separation Process

During photographic color separation:When a red filter is mounted in front of the camera lens:

Red light passes through the filter.Green and blue light are absorbed.Only red light reaches the photosensitive material, forming high-density areas.The absorbed green and blue light produces low-density areas.Therefore, a cyan separation negative can be obtained.

Similarly:

A green filter produces a magenta separation negative.A blue filter produces a yellow separation negative.

Color Synthesis

Color synthesis in printing mainly includes:Halftone dot superposition\Halftone dot juxtaposition.

1. Halftone Dot Superposition

When white light illuminates an overprinted area:

The upper ink layer transmits its characteristic color light and absorbs its complementary color light.The transmitted light then passes through the lower ink layer, which further transmits its characteristic wavelength and absorbs complementary wavelengths.

Examples:

Yellow + Magenta overprint → Red

Yellow + Cyan overprint → Green

Magenta + Cyan overprint → Blue

Yellow + Magenta + Cyan overprint → Black

When cyan, magenta, and yellow inks are overprinted simultaneously, most visible light is absorbed, resulting in black.

2. Halftone Dot Juxtaposition

When white light illuminates yellow halftone dots:Red and green light are reflected.

When white light illuminates magenta halftone dots:Red and blue light are reflected.

Through spatial color mixing:Red, green, and blue light combine to form white light.

The remaining red component determines the perceived color.