Colour Models and Light Properties Quiz

Colour Models

• Colour models are methods for describing colour properties within a specific context.
• They combine light sources with varying intensities, and different dominant frequencies, to create a variety of additional colours.
• Three primary colours are often sufficient for most purposes.
• The range of colours obtainable through a specific method is known as colour space.

Light Properties

• Light is a narrow band of the electromagnetic spectrum.
• The electromagnetic spectrum includes Red (3.8 x 10¹⁴ Hertz) and Violet (7.9 x 10¹⁴ Hertz).
• A ray of light contains different waves with individual frequencies.
• The distribution of wavelength intensities per wavelength is called the spectrum of a given light source.

Colour Fundamentals

• Luminance: The perceived light strength by the human eye.
• Hue: The shade or nuance of a colour (e.g., red, blue, green).
• Saturation: The intensity or purity of a hue.
• Brightness: The subjective psychological measure of perceived intensity, representing the relative degree of black or white mixed with a given hue, visually perceived.

Psychological Colour Characteristics

• Dominant frequency (hue): The perceived colour.
• Brightness: The total light energy.
• Purity (saturation): How close a light appears to a pure spectral colour.
• Chromaticity: A collective property describing colour characteristics; purity and dominant frequency.

Intuitive Colour Concepts

• Shades: Adding black pigment to a colour creates a darker shade.
• Tints: Adding white pigment to a colour makes it lighter.
• Tones: Adding both black and white pigments modifies a hue's purity and brightness.

Colour Systems

• Additive Model (RGB): Light-based model used in emissive devices like TVs, monitors, projectors, displays, cameras, and scanners. Colours in this system come from combining red, green, and blue light.
• Subtractive Model (CMYK): Pigment-based model for printing processes (like printers), and applications involving reflected or absorbed light. Colours are produced by subtracting colours. Common colours for this system include cyan, magenta, yellow, and black.

Complementary Colours

• Additive: Blue is one-third, yellow (red + green) is two-thirds. When combined, they produce white light.
• Subtractive: Orange (between red and yellow); cyan-blue; green-cyan → magenta-red colours; red and cyan are complements.

Colour Models (Cont.)

• RGB Colour Model: The tristimulus theory of vision states that humans perceive colour through the stimulation of three visual pigments in the cones of the retina: red, green, and blue. The RGB model uses these three colours to create different hues. 8-bit/channel gives potential for 16.7 million colours.
• CMYK Colour Model: A subtractive colour model used for printing on paper and creating physical documents. The colours are created by subtracting from white (light). The added black ink (K) improves practicality.
• HSB (HSV)/HSL Colour Model: Cylindrical-coordinate representations of colours focusing on easier intuitive colour selections. HSV (and HSL) rearrange the geometry of RGB to be more perceptually relevant, using Hue, Saturation, and Brightness (or Value, or Lightness).
• YIQ colour Model: NTSC colour coding used for creating composite video signals. Luminance and chrominance (hue and purity) are separate for better perception of brightness and other aspects without affecting the colour.

Lab Colour Model

• Uses human colour perception to create colours numerically.
• Lightness (L) ranges from 0-100, green-red (a) is from -128 to +128, and blue-yellow (b) is from -128 to +128.
• It's a device-independent model; describes how colour looks, not how it is produced.

Grayscale Colour Model

• Produces gray tones; images produced using 8 bits per pixel can contain 256 shades.
• Each pixel holds a brightness value from 0 (black) to 255 (white). The values can be converted to percentages of black ink intensity.

Interface and Applications

• Graphical packages use colour selection tools and methods to facilitate ease of usage.
• Some applications provide colour-pattern guidelines to aid users, such as separating colours to minimise eye strain.
• Better displays use smaller numbers of colours and tints/shades to improve presentation with the intended message.

CSS Colour Property

• CSS allows for easy colour configuration using methods like colour names, hexadecimal values, decimal colour values, and HSL values.

Colour Wheel

• A colour wheel visually represents colours based on their chromatic relationships.
• Primary colours are basic colours that cannot be created by mixing other colours.
• Secondary colours are created by mixing two primary colours.
• Tertiary colours result from mixing primary and secondary colours.

Colour Conversion

• Colour conversion occurs when displaying, capturing images, and printing images.
• Conversion is often performed using colour management systems and colour profiles to ensure accuracy. Colour profiles describe the device's colour space and help to match colours to the original document.

Test your knowledge on colour models and the properties of light in this engaging quiz. Explore concepts like luminance, hue, saturation, and the electromagnetic spectrum. Perfect for those studying color theory and light fundamentals.