However, humans’ sense of well-being has given too little consideration in the past, and the standard does not address it either. For example, just because an office has sufficient illumination from morning to evening, that does not necessarily make it the ideal environment for the employees working in it. Nowadays, it is beyond dispute that we always feel most comfortable – and are therefore most productive – when our working environment comes as close as possible to the natural cycle of day and night: the so-called circadian rhythm.
Rods, Cones and Ganglion Cells
The reason for this is a third class of photoreceptors, only discovered comparatively recently. While rods and cones perceive light-dark contrasts, as well as colors via embedded visual pigments, the ganglion cells are not responsible for image recognition. Although they are also sensitive to light, they use this information to regulate the human day/night cycle. The ganglion cells are thus responsible for the fact that we get tired and go to sleep at a certain time in the evening – not at noon, for example. Conversely, this means that for human beings, there is no single ideal type of light, since 500 lux and 5000 K do not have the same effect on us at eight in the morning as they do at three in the afternoon.
