How VISUAL COMFORT
Find out more about the ways that human beings identify and react to different light levels...
THE PHYSIOLOGICAL ASPECT
The human eye is a highly complex, light-sensitive organ. It is made up of:
(1) A diaphragm, which adjusts the total quantity of light entering the eye – the iris and pupil.
(2) A lens, which adjusts the focus.
(3) The rods (black and white low-light sensors) and the cones (color sensors).
(4) Synchronization cells – the photosensitive retinal ganglion cells.
Our retinal ganglion cells (which were only identified about 10 years ago) don’t actually contribute to the formation of images, but are responsible for ‘non-visual effects’. These are key for our biological clock – the part of our brain that regulates our sleep – affecting wake rhythms, our heartbeat, and the workings of our organs.
As a result, light has a direct effect on the regulation of various biological functions, such as sleep, mood, alertness.
The sun (or an electric light bulb, if the light source is artificial) emits propagating energy, of which a limited range of wavelengths, included between infrared to ultraviolet, is perceptible to the human eye as light.
Ultraviolet (UV) radiation, with shorter wavelengths and a higher frequency, is that which colours the human skin. The infrared radiation, with longer wavelengths, is felt as heat.
Our perception of light is determined by the amount of radiation energy that enters the eye and the spectrum of this light.
THE PHYSICAL ASPECT
VISUAL COMFORT is a subjective reaction to the quantity and quality of light within any given space at any given time. It’s the interaction of a physical phenomenon (light) with a biological organ (the eye) that allows us to see.
The concept of visual comfort depends on our ability to control the light levels around us. Both too little and too much light can cause visual discomfort. Just as importantly, changes in light levels or sharp contrast can cause stress and fatigue, as the human eye is permanently adapting to light levels.
Light has qualitative aspects, as well as quantitative. The light source, distribution, tone, colour and intensity all play a role in our perception of light quality.