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Monday, March 1, 2004

Tame Lighting Extremes

Nature often serves us splendid scenes, but with light that won‚’t cooperate with our camera‚’s and film‚’s abilities. Here‚’s how to bring those conditions under control.

LTame lightninget's face it—the world isn't built for the convenience of the photographer. We've all been to a location with a fine composition right in front of us, but the light makes the contrasts too extreme for us to capture it with the camera.

The technology of photography, film or digital, has its limitations, and one of the biggest is dealing with a limited ability to capture a range of tones, compared to the infinite variety of light we actually see in nature. Ansel Adams developed his Zone System of exposure and development specifically in response to this challenge. It allowed him better control over translating real-world contrasts into the limited contrast range of film and prints.

You don't have to learn the Zone System to deal with lighting extremes today. While there are a number of possibilities available to the photographer, we've chosen three techniques that will help: filters, flash and digital processing.

Filters Still Work In A Digital Age

With the advent of digital, some photographers have begun to believe the computer can do anything, including eliminate the need for filters. Of course, the traditional photographer who never uses a computer will find some advantages to using filters, but even the digital-savvy photographer should have some filters in his or her camera bag. While the computer can do a lot, especially with the two-exposure (or more) system of tonal-range control, it has limitations. If you can control the tonality of your photo while actually photographing the subject, you'll have less work to do later in the computer. And for some scenes, it's easier to be sure you've captured the tonalities with which you need to work in one exposure than trying to make multiple photographs work together later.

Filters Still Work In A Digital Age
The difference between sky and foreground during twilight periods is extreme. Correct exposure on both the sky and foreground is usually impossible without the use of a graduated filter. Right: Here, the rock face in the foreground is correctly exposed, but the sky is blown out. Below: Applying a graduated neutral-density filter darkens the sky, but leaves the correct exposure on the rock face.
The key filter every photographer should own is a graduated neutral-density filter (also called graduated ND, grads and split neutral-density or ND filters). It's a huge advantage to the photographer who wants to get the best exposure from an extreme situation.

Many of you know and use this filter, but for the beginner, here's a quick explanation. The graduated neutral-density filter is clear in one half and gray (neutral density) in the other. The two areas blend together in a gradation of tone in the middle of the filter. The filter rotates inside its mount, allowing you to move the dark, neutral-density area over the bright part of the scene. The clear half of the filter now sits over the darker part of the scene. The result is that the darker part of the scene comes through directly to the film or sensor, while the brighter part is dimmed by the ND filter. The blending in the middle hides the change. This allows you to capture a scene with a greater range of brightness than could be handled normally.

The most common way of using this filter is with landscapes. The sky is frequently much brighter than the land, making photos look unnatural compared to what we see with our eyes. With a grad, you move the ND portion over the sky so that its brightness is dimmed, allowing the sky to better balance with the ground. If your filter is of the screw-in type, you're limited to rotating the filter, which may or may not match your actual scene. With rectangular filters, you can slide them in their mount to better match the horizon.

Filters Still Work In A Digital Age
Graduated neutral-density filters aren't only for use to darken a sky. Right: The rock is in shadow while the meadow at the top of the frame is lit by bright afternoon sun. The result of exposing the rock correctly leaves the top of the frame much too bright.
Below: A graduated neutral-density filter alleviates the problem. Note that the shadow line runs at a diagonal across the frame.
In order to get the best result from the filter, it's important to match the line of the split to the shadow line.
The late Galen Rowell was a master of using the graduated ND filter in the landscape. Look at any of his photos and you'll see rich colors in both sky and ground, usually impossible to achieve with a straightforward shot of the scene. He'd even put multiple filters together to intensify their effect, moving them slightly to be sure the blended areas fit the scene.

Graduated ND filters come in a variety of strengths that affect the intensity of the effect as well. The most common are one- and two-stop neutral densities; the dark areas of the filter (the neutral-density part) will knock down the brighter parts of the scene by one or two stops. If you were to buy only one, I'd recommend the two-stop model, as it will work on more extreme conditions. The more expensive graduated filters tend to give you the most neutral density in the dark part of the filter, which can help keep your colors clean.

In addition, graduated filters also come in colors (usually in one- and two-stop strengths). These can be used to both reduce the brightness of an area and enhance the colors. For example, a blue grad can be used when the sky is a washed-out blue; it will darken and increase the color of the sky. An orange or tobacco color grad can intensify a sunrise or sunset.


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