Describing Colour
• Words we might use when naming and describing colours:
• ‘shade, hue, warm, tone, bright, dim, pale, intense, vivid, rich, saturated, cold, strong, wishy-washy, glowing, colour, flat, weak, muddy, soft, vibrant, luminance, bold, tint’
• Very subjective - influenced by perception and characteristics of illuminating light source.
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Hue, Saturation, Value (HSV)
The HSV model is based on the following concepts
• Hue - this is what most people would refer to as the colour or shade. Red, yellow, green and blue are hues.
• Saturation - this is a value that represents where the colour is on a scale from achromatic white to the pure hue.
• Value - is the attribute, sometimes referred to as brightness, which determines how intense the colour is on a a scale from black to the pure hue.
Colour Models
• Additive Synthesis - Start with no light. Add red green and blue light to make white and complementary colours
• Subtractive Synthesis start with white light. Subtract red green and blue light to achieve complementary colours and black
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Colour Models:RGB
• Display devices generally use a color model called RGB.
• Stands for Red-Green-Blue• Based on the additive synthesis model• RBG colour value specified in three bytes
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Colour Models:CMYK
• Cyan-Magenta-Yellow-Black, and pronounced as separate letters. CMYK
• Based on the subtractive synthesis model• CMYK is a colour model in which all colors are
described as a mixture of these four process colours.
• CMYK is the standard colour model used in offset printing for full-colour documents. Because such printing uses inks of these four basic colours, it is often called four-colour printing.
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CMYK Subtractive
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Subtractive color: Illuminate objects that contain dyes or pigments that remove portions of the visible spectrum.The objects may either transmit light (transparencies) or reflect light (paper, for example).The subtractive primaries are C, M and Y. Cyan absorbs red; hence C is sometimes called "minus red" (-R). Similarly, M is -G and Y is -B.