Do we even need to debate the importance of light in our lives? Imagine the earth without the sun, which gives it light and heat. A warm summer’s day is one of life’s pleasures, and even in winter when the warmth of the sun may not be as apparent, the light it delivers gives us some inner comfort. If all that sounds too far fetched, then imagine yourself in a dark room. While it may be initially be calm and peaceful, after a prolonged period a sense of isolation creeps in and the eerieness becomes disturbing and the mind starts to play tricks on you. For this reason prisoners of war are often keeps in prolonged periods in dark rooms – lack of light is a form of torture.
Of course, too much light can also be a problem. It forces us to narrow our vision to filter out the excess light, and the tension we can feel in our face is not a pleasant experience. When the car driving towards you has its headlights on full power we wince at the thoughtlessness. Too much light also strains the eyes. Remember the advice not to look directly into the sun? Or when you are looking at your phone in the dark at night? What we need is optimum lighting to serve the functions we require it for.
There are many categories we can discuss light in terms of. These categories and divisions help us to distinguish between the functions and characteristics of the different types of light in order to help us determine what we need. Lighting in general can be divided into the categories of indoor and outdoor lighting. Lighting can also be divided into the categories of local lighting and general lighting. Local lighting refers to light at a specific area, while general lighting refers to what is perhaps referred to as background or non-specific lighting. These four categories may have a degree of overlap to them. Are these divisions necessary? Definitely. You speak of a table lamp as a kind of indoor lighting where the local light is more powerful than the general lighting. The lighting you need indoors in the kitchen may be a mixture of focused and non-focused lights where the strength of local and general lighting vary. If you are looking for an outdoor light where the local illumination is stronger than the general one, then it is assumed you will be looking for a spotlight or searchlight. Knowing these categories help us to determine and discuss lighting needs with more clarity.
Whatever our lighting needs, we need to consider how direct or indirect the lighting is. The amount of light to an area can be wholly direct or wholly indirect, or a combination of the two. Even when used in combination, there are terms to distinguish between the different levels of combination.
Direct lighting is lighting where most or all of the source light falls onto the object. Reflecting surfaces have little or no effect at all. This system is perceived as efficient but you may get issues such as shadows if the lighting source is not sited correctly. A traditional table lamp is an example of this kind of direct lighting. Because the lighting is direct, prolonged exposure can also be very taxing. Even if you are not looking at it directly, reflection of the light by surrounding surfaces can be very strenuous on the viewer. If you shine a direct light into a reflective surface, for example, a table lamp onto a laptop screen, it is not good for your eyes in the long term.
Another type of lighting is diffused lighting. Diffused lighting is different in the way that most of the light to the object is broken up. The direct focus of the light onto an object is not present, but the lighting is ambient, broken up, softer, and kinder on the eyes. For this reason diffused lighting is used in certain residential settings to give an impression of warmth.
Another method of lighting is indirect lighting. This kind of method means that none of the source light falls directly onto the object or area. Instead, it is directed upwards and the surfaces reflect the light downwards or away. Indirect lighting is useful in avoiding glare, however it can make huge electrical demands because the light arrives indirectly as a secondary source via reflection.
Sometimes lighting demands are best achieved using a combination of lighting methods. These are termed semi-direct or semi-indirect methods of lighting. In both methods, light to an area is both by direct and indirect means, but semi-direct lighting has a greater proportion of direct light while the reverse is true of semi-indirect lighting. An uplighter may be an example of such combination lighting, and whether it is classed as semi-direct or semi-indirect depends on how transparent or translucent the material itself is. If it is entirely dark and does not allow light to pass through, then it would be lighting the room by indirect methods.
The different kinds of lighting methods are not specifically constrained to different objects; as we have seen before, an uplighter may either light a room semi-directly, semi-indirectly or indirectly. A bulb may light a room directly or it may do so doing in a diffused way.
We speak of lighting as being suited for indoor or outdoor purposes. Whatever the purpose, there are required differences in intensity between local specific areas and general areas, and there are different ways to achieve the desired level of light, using direct, diffused, indirect or combination lighting.
Imagine you are watching a classical music concert. There is a soloist playing the piano while the members of the orchestra are around him. The conductor stands in the front center. How do you light up the stage? The local lighting demands for the pianist and conductor are greater than the general lighting. But you can’t just focus a spotlight directly on the two individuals because the reflection of light from the piano might deflect the sharp glare back to the audience. And while a spotlight may bring out the conductor to the audience, it might also cast a huge shadow over the string players, especially the viola section. And in the course of the performance, various members of the orchestra may have solo sections of music to play and the light must fall subtly on them such that the audience can pick out who is playing. And over the course of the performance the lighting must adjust in intensity, the general lighting to an area decreasing slightly as local lighting increases slightly in a complex interplay, or the audience will have a headache if the level of light is too much. The length of the performance can also be an issue to consider when it comes to measuring the lighting intensity. So lighting is a complex task that engineers don’t get enough credit for – one thing for sure though; it is not just some guy turning lights on and off!
About Me: I give home piano lessons in Crouch End, London N8. For a post related to lighting on my other blog click here.