“Photography is 50% photographer, 40% light, and 10% equipment.”
Lighting conditions can be classified according to the dominant type of light: direct, diffuse, or ambient. Each poses its own challenges and has its own opportunities, and demands different approaches from the photographer.
Direct light dominates
One of the most difficult lighting situations is when direct light dominates.
The typical example is a clear, sunny day. Shadows are sharp and deep, the scene often has too much dynamic range (difference between the darkest and the brightest areas) to be captured without either blowing out the highlights or losing the shadows, and three-dimensional shapes tend to get flattened into paper cutouts. The main challenge is to deal with the dynamic range, though. Three strategies that can work in direct light include:
Place your subject between you and the light, and expose for the shadows. The light will outline the subject, and even if the outline gets blown, it won’t matter very much. The ambient light will fill in the shadows, and the outline will give it contrast and liveliness. In addition, if your subject is a person, their expression will be more natural from not squinting at the bright light source.
Position your subject near a white or neutral gray object lit by the light source. This will work as a diffuse light, giving three-dimensionality and generally much more pleasant lighting. If you have one, use a movable reflector, such as a big white chunk of styrofoam.
Use your camera’s flash (built-in or separate) directly on the subject.
This will decrease contrast and make for a better tonal balance, although the picture will still look flat and rather two-dimensional.
In addition, black and white negative film is a good choice for sunny days: it has up to fifteen stops of dynamic range, which is enough for almost any lighting situation.
Ambient light dominates
A typical situation where ambient light dominates is an evenly overcast day. Shadows are not readily apparent and objects appear somewhat two-dimensional.
This light is technically easy, as there is little contrast: the camera’s auto-exposure system will get the exposure on the nose every time. However, the pictures will easily turn out boring and flat-looking.
The trick to taking good pictures in ambient-light situations is to find things that stand out in spite of the light rather than because of it. Instead of trying to bring down contrast, you should find subjects that have more of it.
Look for objects with bold color or shape, or deeply shadowed areas such as gateways or windows — this way, you can turn the ambient light into a diffuse light source, which is usually much more interesting.
Diffuse light dominates
Diffuse light is “good light.” Contrast levels are manageable, the light brings out three-dimensionality, and the pictures have a very pleasant, soft quality.
A photographer usually actively seeks out diffuse light: the famous “magic hour” before sunset or after sunrise is just such a situation — the sunlit horizon acts as a huge diffuse light source, with a lovely, warm color cast to boot.
Diffuse light is at its best coming from an angle to the subject: neither fully backlit nor front-lit. Carefully engineered light is usually dominantly diffuse: when you see a studio scene, over nine times out of ten, it is carefully lit with diffuse light, possibly from multiple sources.
Light scattered by dust, raindrops, fog, clouds, haze, or smoke is something of a special case. Sometimes it is undesirable, such as for a high-altitude landscape. Haze makes it look murky and flat.
UV filters and especially polarizers can help cut through haze and make the scene clearer. However, more often it’s better to make a virtue out of a weakness and actively seek to exploit scattered light. It can show up light beams, create a wonderful sense of distance and depth, and create a great deal of atmosphere.
Don’t try to take a picture through the fog or the haze: take a picture of the light flowing through the fog or haze.