Properties of Artificial Light- II
by William Lulow
So, the second property of artificial light is that it must be controlled. For instance, one 500 watt floodlight mounted in a socket with a metal reflector of 12″ or so in diameter, produces a very bright, harsh light. The reflector acts to direct the light in a fairly broad pattern (somewhere in the vicinity of 100 degrees. [See diagram of several reflectors and their coverages].
This would be a broad enough pattern to light a person’s face fairly well. If we wanted to light just the person’s eyes say, we would obviously need a somewhat narrower reflector to keep some of the light off the other facial features. This would call for a smaller, narrower reflector. Probably something like 4″ or 5″ would do the job. Another way to control the light from a large reflector is to set up barn doors or “gobos.” A barn door is simply a dark card which is placed over part of the light to cast a selective shadow on the subject. It can be moved back and forth or in and out so the effect is just right. Similarly, a “Gobo” is a black card which “goes between” the light and the subject in much the same way as a barn door. Obviously, the spread of the light from the two different reflectors or the “gobo‑ed” light would be very different. In the same way, light from the same reflector can be different in quality as well as direction and intensity. For example, if I took that same 500 watt floodlight and put a piece of spunglass over it, the resulting light would be softer, less harsh and more diffuse. The spunglass would act as a diffusion material, scattering the light rays even further and producing that softened effect. This can be very useful to the portrait photographer who is trying to flatter the subject with very soft light. (More about flattery later). Light can also be altered by each of the other tools mentioned above. There is a great difference however, in the quality of light given off by strobe light (Electronic Flash) and continuous light (hot Light). Strobe light is non‑continuous light created when a generator, consisting of several large capacitors, resistors and electronic relays, stores electricity until it is needed. When the photographer snaps the shutter, all the stored electricity is routed through the flash tube in the flash “head.” Gases in the tube glow very brightly but very briefly when the electricity hits it. This all produces a very short but intense “flash” of light. This single flash is many times brighter than our 500 watt flood light. Also, due to the short duration of the flash, (usually 1/400th of a second or shorter) it is able to “freeze” most action in the photograph. However, the effects of the light are exceptionally hard to distinguish for the naked eye. Another difference between hot light and flash is that the former is on all the time and the latter is on only when the picture is taken. If you have ever sat under a 500 watt floodlight you can imagine how uncomfortable it could get for a subject sitting for a whole portrait session with it on. Electronic flash therefore, is usually much more comfortable for the subject. Even though this is a distinct advantage, the disadvantage is that electronic flash units are much more expensive than hot lights and it takes a lot of power to run them. It is also difficult for the photographer to preview the lighting setup unless he or she shoots a test shot and previews it on the camera’s LCD screen. These days, I use a laptop to preview my lighting setups. Sometimes I find that the camera’s LCD is too small for an accurate examination.
All the other types of lighting accessories, basically alter the type or quality of light that the unit puts out. Grids channel the light in only one direction, Light banks simulate soft, outdoor, cloudy bright conditions, Reflector cards add brilliance and fill‑in light to an image. Umbrellas create soft, diffuse effects in a limited space because the light bounces off the umbrella and then hits the subject. Umbrellas have become very practical accessories because of their portability, the limited amount of space in most studios and because of the very soft illumination that they give. They are also foldable and do not take up much room in the studio. It would take a light of considerable size and weight to give the same type of light that an umbrella gives. It is true that a large metal reflector the size of the umbrella would be more efficient, but it is often necessary to trade efficiency for ease of handling in most practical applications of lighting.
This image was made with a small, directional reflector attached to a strobe head. The light was aimed in one direction. This is known as a “Rembrandt Lighting.”