Lighting 102: In the Zone

Abstract: On any lit object, there are four distinct zones of light.

Photo by Kenneth Lau

When you light any three-dimensional object, you create various zones of light and shadow. It doesn't matter if it is a face or a tomato. So today let's learn from this tomato, photographed by Strobist reader Kenneth Lau.

Looking at the photo above you might think, "Two zones: light and shadow." But if you look more closely, there are actually four lighting zones on this tomato.

Let's start off with the shadow area. That's pretty self-evident. It's the area on the tomato where the surface cannot see the light source.

And that big red area up top is, obviously, a highlight. But it is not the only highlight, so we have to differentiate it. Dean Collins, a photographer who was my idol early in my career, called it the diffused highlight area.

I like that, because it explains that this is the area of the tomato which is reflecting diffused light back to our eye. And properly exposed, the diffused highlight shows us the true tonality of the subject.

But there are still two more zones.

Next is the area between the diffused highlight and the shadow. That's where an ant, walking across the tomato, would be experiencing the sunset of our light source. From lit area, to not-lit area. We learned all about that in the previous post.

This zone is called the diffused highlight to shadow transfer area.

A mouthful, to be sure. But that is the best description of what it is. And learning to think of it in that way well help you to better understand and control it.

The final zone is the other highlight area — the area that shows the reflection of the light source itself. That's called the specular highlight. This zone is affected by both the quality of the light source and the surface quality of the subject itself.

That's why you can tell if a can of Coke is ice cold without touching it: the edges of the specular highlight become softened, or even matte. This tells you that there is condensation forming on the can, which tells you the Coke is cold. And by manipulating that specular highlight, a food photographer can make you lust after an ice cold Coke in a photo.

Being able to control the specular highlight in portraiture is a very handy thing. It will give you all kinds of possibilities, and solve many problems. We'll talk about that more in the next post.

But first, a few things to keep in mind about our four zones:


• Specular highlights are reflections of the light source, plain and simple. They reveal for us not just the quality of the light source, but also the surface texture of the subject.

• To lessen the intensity of a specular highlight, spread the your light out over a bigger source. With a diffuser, for instance. The light will be dimmer per square inch, so the specular highlight will also be bigger and less intense.

• Properly exposed, the diffused highlight of a black object is still black. Meaning, the diffused highlight is the same tone as the shadow. So we use specular highlights to show both shape and form in a dark object.

• Conversely, when shooting white objects we use shadow to reveal shape and form.
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EXERCISE:

Grab a tomato. Walk over to an open-shade window (i.e., no direct sun). Hold it in the light and examine the four zones mentioned above. Study how the light source interacts with the tomato to inform you about its surface qualities.

Breathe hot air onto the tomato and see how the diffused-to-specular highlight transfer area changes with the presense of matte condensation.

Next: Controlling Specular Highlights