Shedding Light: Continuing the lighting journey – monthly column featured in Sparks Electrical News

Shedding Light by Philip Hammond is a monthly column featured in Sparks Electrical News by Crown Publications, we he discusses a variety of  industry topics from the world of lighting such as standards and compliance, lighting applications, the role of light in our lives and more…

Oh, my word, we are a third of the way through 2022. The expression – “Time and tide wait for no man” was written by Geoffrey Chaucer, author of the well-known Canterbury Tales. Remarkably, he is often referred to as the father of English literature! We will continue our look at the Visual Functions of the human eye.

Brightness Response

When we enter a room or merely move our head in a known environment, the eye tends to seek a state of equilibrium which suits the general brightness conditions. This involves some photo-chemical action within the eye but it is most affected by the action of the iris in front of the lens. The iris opens as general brightness of the scene is low and closes when it is high. But there is a time lag in this re-adjustment, especially when there is a change from high levels of luminance to low (luminance is the physical or photometric correlation of the psychological sensation of brightness). This is an important aspect of lighting design, particularly in a mobile situation such as when driving a vehicle, because immediate dangers can occur without them being recognized when changing from a bright environment to a dark.

Colour Response

Colour is in the eye of the beholder. Nothing on this planet has any colour. You perceive colour through the wonder of the colour photoreceptors in your eyes. The eye is especially responsive to differences in colour under high levels of lighting where the cones in the eye are active, but it is deficient under low lighting levels when the rods alone are activated. It is important to understand the effect of light and colour on the visual scene. For example, colours are not interpreted identically on the retina of the eye. Some studies indicate that a green object is imaged clearly on the retina, a red object of the same size would be interpreted as being slightly larger behind the retina and a blue object slightly smaller in front of the retina. This explains the psychological interpretation of warm colours appearing to advance and cool colours to recede and diminish in size. In some cases it may be important to take into account that 8% of men and 0,5% of women have alternative vision (previously known as colour blindness which today is known to be untrue), the most common being the difference of the red and green sensitivity.

Continue reading the full monthly column of Shedding Light: Lower lighting loads in times of loadshedding by Philip Hammond on Sparks Electrical News HERE.


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