The way light plays across a subject can dramatically change your perception of it. Does your garden appear flat and one-dimensional or richly layered? Does texture appear or disappear in the sand on the beach? Are facial contours accented or hidden? Consider two aspects of light: the size of the source in relation to the subject and the direction from which the light strikes it. This month I’ll discuss how the size of a light source affects its quality. Next time I’ll cover the effect light direction has on revealing shape and texture.
Small Light Sources are Hard-edged
What’s the biggest light source you can use? You might think it would be the sun. It’s about 1.4 million kilometers (870,000 miles) across. You can’t get much bigger than that. Yet from a photographer’s perspective the sun is a very small, or point source, because it’s far away. The absolute size of the light source is less important than its apparent size relative to your subject.
A big light source a far away from a subject becomes a small source. Conversely, a small speedlight held very close to an insect or small flower becomes a large source. It doesn’t matter whether the source is natural, sometimes called available light, or a flash unit you bring to the scene. It’s the size of the light relative to the subject that controls the quality of the shadows.
Small light sources create sharp-edged shadows. Think about what your own shadow looks like on a bright sunny day. You’ll see a sharp transition between light and shade and the brightness difference between shaded and not shaded is large. As a photographer you can think of small lights as creating harsh light. Contrast is increased.
Small lights can be dramatic and may be the right tool to create a mood. Think film noir.
Large Light Sources Make Soft Shadows
The ultimate giant soft light source is a cloudy sky. Drag a layer of clouds between you and the sun and that harsh point source will be diffused. Sunlight bounces around among billions of water droplets and then comes out the bottom of the cloud deck uniformly. There are no shadows on the ground at all. That’s because the light is coming from all directions at once. Every point in the sky has about the same brightness.
This soft, directionless light is gentle and flattering. You can see detail in both the bright and dark parts of an image. In a portrait, soft light hides wrinkles and other signs of aging. In a flower photo like the autumn garden scene above you can see all the natural color in both brightly-colored blossoms and dark green foliage. Contrast is reduced.
My favorite light for photographing gardens, native plants, and many outdoor portraits is a bright overcast sky. When God and nature don’t oblige, then I look for ways to soften and diffuse the light I’m given.
Often the simplest solution is to photograph in the shade. Open shade, where the subject is lit by indirect light from the sky, has a similar quality to a cloudy day. Just remember what I wrote about last month regarding colors appearing more blue-green in the shade.
Another outdoor solution is to create your own shade, or to diffuse the light. I carry a collapsible diffuser with me when I’m photographing flowers. I call it my “portable cloud” and it opens up to about 36×48 inches, big enough for most plants or for an individual portrait. Mine is a Westcott 1-stop silk. I still get shadows but they’re soft, diffuse, and open. It cuts the light by one stop. There are other brands and models, including the popular Photoflex LiteDisc. The Photoflex cuts the light by two stops and I’ve found the light is too diffuse and flat for my taste. I still have one but don’t use it much. Some photographers make their own diffusers from a shower curtain or thin white fabric mounted on a frame of PVC pipe.
When I’m working in the studio I use a variety of tools to make my light sources bigger: bounce a strobe off a white umbrella, filter it through a large softbox, or bounce it off the ceiling. For location portraits I’ll often use a strobe in an umbrella as either my main or fill light to control the shadows on your face.
When it comes right down to it, shadow size, darkness, and position, together with color, are the defining qualities of light. Last time I wrote about the color of light. This time I covered the effect of the relative size of a light source on apparent contrast, the darkness and edge quality of the shadows. Next time we’ll move the light around and see how its position shapes and sculpts a subject.