The Colour Phenomenon

Published on: Sunday 15 December, 2024

Can you see in darkness?
Do the colours you see exist during darkness?

Colour is a SENSATION

For much of history, most of us believed that colour was something 'absolute', an inherent property of objects. Even today, we continue to see, perceive, and interact with colour as though it’s something that simply exists out there in the world—something inherent and unchanging.
It makes life easier to think of colour in this way. But, to truly understand colour, manage it, and control it, we need to grasp how the sensation of colour actually happens.
Yes—colour is a sensation.

All sensations occur when our sensory organs are stimulated. The stimulus for our colour sensation is light, and the sensory organ involved is the eye.
The object you look at to see the colour is simply the object.

Colour of an Object

When light hits an object, part of that light is absorbed, while the rest either gets reflected or transmitted, depending on the nature of the object.
It’s the unabsorbed light—the light that is reflected or transmitted—that reaches our eyes and generates the sensation of colour.
In other words, the colour we perceive from an object is determined by the portion of light that the object does not absorb.

While this may seem obvious and simple, many of the challenges we face in colour management stem from forgetting or overlooking these basics.

 

Genesis of Colour and Varying Sensitivity of Colour Sensors

When light enters the eye, it’s bent and focused onto the retina, a layer of neural tissue at the back of the eye. The retina contains light-sensitive cells that encode information about the intensity and wavelength of the light that strikes them, sending this information as neural signals to the brain.
Interestingly, the sensitivity of these retinal cells to the visible wavelength range is not uniform. In other words, the cells that encode wavelength information are sensitive to different wavelengths of light in varying degrees.

This system of sensors, or what we refer to as colour vision, allows us to differentiate wavelengths of light—and, in turn, objects—based on their unique emittance or reflectance spectra. These spectra are almost unique to each object.

We will delve into this concept further in the ‘Vision’ segment, but having this foundational understanding will make it much easier to grasp light sources and how we measure them.

In summary, to see the colour of an object, three things must come together:

  1. A light source – the provider of the stimulus
  2. The object – the thing whose colour you see
  3. The observer – your eyes
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