The nature of light itself is still the subject of much speculation. Current theories explain light by giving it the properties of both waves and particles. We will deal primarily with the wave theory; this explains the aspects of light, such as wavelength and frequency, that concern us in colour photography.

The easiest way to understand light waves is to imagine holding a string that is fixed in position at the other end. By vibrating this string, you create waves traveling along it. The faster you vibrate it, the narrower the distance between the crest of each wave. The slower you vibrate it, the longer this distance. This spacing between the points is known as the wavelength.

It is this difference that creates the different colours within the spectrum. The brightness of the light is due to the amount of energy produced by the light source. While this has an influence on photography, it does not directly affect the colours produced.

Light waves are the visible part of a much larger group of waves known as the electromagnetic spectrum, which includes X-rays and radio waves. The  range that is present in daylight is shown below. This ranges from the short-wavelength ultraviolet to the longer-wavelength infrared, with the visible portion in between.

Diagram of Light Waves by www.antonine-education.co.uk

While our eyes cannot see ultraviolet or infrared radiation, these can have an effect on the image produced by both digital sensors and film. In most circumstances, it is undesirable for the image to register radiation outside of the visible spectrum. However, it is useful for both scientific and artistic applications for producing images of a world beyond our visible experience.

Adapted by Caley Taylor from Chris Rutter’s “Color Theory Fundaementals for Digital Photography”