Rangefinder Magazine
Features - June 2001

Portrait Photographers’ Workshop by David Bently, M. Photog.Cr.
White Light Can’t Wrap

For years I’ve heard photographers discuss beautiful soft wrap-around lighting in such glowing terms, I sometimes thought they were talking about women… beautiful to look at but difficult to understand.

In fact, physicists tell us that light is sometimes best understood if we think of it as a wave phenomenon, although sometimes thinking of it as individual particles seems to make the most sense, depending upon what effect we are trying to explain. Speaking of explanations, I’ve even seen a few photography instructors try to demonstrate how light wraps; however, from all I’ve seen and learned through the years, portrait lighting is strictly a straight-line event! Quantum theory and diffraction aside, our average client is neither narrow enough to diffract light nor massive enough to have a noticeable gravitational effect on it. By this I mean, portrait light travels in a straight line being reflected, diffused, attenuated, or blocked but never, never wrapped! Once this is accepted, lighting is much more understandable, predictable and manageable.

We can look for light, add to existing light, reflect it, change its color temperature, or block it to create our vision of the scene. Most of what you need to know about how portrait light behaves can be learned from watching a good game of pool.

Figure #1 depicts a typical softbox portrait light arrangement. The contained light source “A” emits light in all directions within the box. Some light travels directly to the front diffuser, and some is reflected internally before eventually striking the front diffusion panel. The outer surface of the diffuser becomes a light emitter with the light being radiated in a hemispherical fashion from each area of the fabric. You can test this by simply looking at the front of a softbox. If you can see the front surface, light is coming off it. Some light falls on the subject (the round-faced lady shown in the figure), but most of it travels off to who knows where. Actually, my wife Susan explains that this “stray light” is all accounted for; some hits the background, some hits the floor and ceiling of the studio and some falls on any reflector we place in its path.

Back in the softbox, each of the diffuser emitters in the front of the box has a chance of sending light to the subject in the area “H” from points “C” to “C.” The area “T” from points “C” to “D,” however, receives progressively less light as we work our way around her face to the back “M” (which no direct light can reach).

As we move from “C” to “D,” less and less of the softbox face is capable of lighting this area. The size of area “T” is what we call our measure of the “softness” of the light. This is actually the transition from highlight to shadow. If it is large, we say we have soft portrait light. If area “T” is small, we say we have hard light.

Figure #2 shows what happens when we move the same softbox farther from the subject. We see “H” become larger, and “T” become smaller. We can’t lose sight of the fact that the total amount of light hitting the subject is smaller but more importantly, the distribution has changed, and the light is said to be harder (area “T” is smaller). In either case, the light does not wrap; it just does its straight-line light thing.

By the way, the relative variation of “H” and “T” is suspiciously reminiscent of what we see when we change lens focal lengths in portraiture. Could it be we could also change the apparent shape of the face with the size/closeness of the light source? Sounds like something for us to investigate. We asked Courtney Hennesy to help demonstrate this effect for us.

Photo #1 shows Courtney photographed with the softbox close, as it is in Figure #1. This is the preferred location for most photographers using a softbox for portraiture. The justification is that area “T” is greater. The transition from highlight to shadow is larger, resulting in soft and presumably flattering light. We should also be aware of the relative size of area “H” that slenderizes the mask of the face.

In Photo #2, a fill light was added to make the finished lighting setup more conventional.

In photo #3 the softbox was pulled back more like the position shown in Figure #2. This results in more harsh (hard) light because the area “T” is smaller. We also notice the area we call “H” has expanded, resulting in the appearance of a broader facial structure.

In Photo #4, again a light was added in the fill position. It seems the apparent shape of the face was altered by the distance of the softbox from the subject. This is separate from the change in softness of the light. This effect is yet another tool available to the portrait artist photographer whose ultimate goal is to produce the most flattering image of the subject.

For two decades Bentley Studio, Ltd. has been recognized as the source for artistic photographic imagery. David and Susan Bentley are nationally acclaimed photographers and have both earned the national degrees of Master of Photography and Photographic Craftsman. David’s area of specialization is in portraiture, with a major part of his acclaim coming from his wedding and family photography. He is frequently published in leading photographic journals.