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Cora Banek, Georg Banek



Targeted Contrast Control

By Cora Banek, Georg Banek
Published by Rocky Nook

How do you ensure that you're capturing the full tonal range of your scene? You can use spot metering to measure the contrast range of an image. Find out how with this excerpt from Cora and Georg Banek's Rocky Nook book Learning to Photograph.

This excerpt from Learning to Photograph is provided courtesy of Rocky Nook. To purchase the book, visit Amazon.com.











There are three ways that your subject’s contrast range can stack up against your camera’s ability to capture it: the subject’s contrast range can be smaller than, equal to, or greater than the capacity of your sensor. Each situation requires specific and targeted action:

  • When image area exhibits a smaller contrast range than your sensor, your task is easy. You simply control the exposure so both the brightest and the darkest points in the image are within the dynamic range of the sensor. With normal exposure metering based on a mostly neutral gray part of the subject, you’ll stay within this range. When in doubt, opt for slightly more exposure to avoid noise in the dark areas. Or if you want to avoid the lighter, desaturated colors that result from a brighter exposure, you can slightly underexpose the image to get more saturated and intense colors.
  • Things get a little more complicated when the dynamic range of the subject more or less matches the dynamic range of the sensor. Here your goal should be to regulate the exposure so the contrast of the subject is exactly captured. Base your metering on a medium brightness and take a close look at the histogram to make sure the brightness values range from the extreme left to the extreme right sides of the graph. When there are no dark values, reduce the exposure; conversely, if there aren’t any bright values, increase the exposure.
  • When the contrast of your subject exceeds your sensor’s dynamic range, it’s impossible to capture the entire range of contrast. You will lose detail and visual information in either the light or dark areas of your image; you must decide which option compromises your image the least. Alternatively, you could attempt to decrease the contrast range of your subject by, for example, brightening the dark areas with fill light or shielding light from the brightest areas.

As long as the contrast of the subject is not larger than the dynamic range of your sensor—which is usually about nine stops—you can capture all the image information. If you don’t expose your image incorrectly (a), you can target your exposure either on the highlights (b) or the shadows (c). Many times, however, you will encounter a subject whose contrast exceeds the dynamic range of your camera. In these cases at least some of the image information will be lost in the highlights or shadows (d). Your job is to determine the sacrifices that are least harmful to your overall image.

You can use spot metering to measure the contrast range of an image. Meter the brightest and darkest points in your image and calculate the difference between the aperture/shutter speed combinations in whole stops. This process is somewhat laborious, but it can be helpful with studio photography and architecture or landscape images. You can produce digital negatives that contain a maximum amount of image information, which can be used to produce high-quality, fine-art images

Range of Contrast for Other Media

Other media have their own dynamic ranges. When you compare a monitor, a projector, and paper, you can see that paper is the most limited in terms of dynamic range. This makes it impossible to represent all the levels of brightness you see on a monitor in a print. When a photo is printed, the tonal values are adjusted as much as possible. The difference between the huge dynamic range of the human eye and the limited dynamic range of a camera sensor is why the sky above your subject may appear rich with color when you take a picture, but it looks like a blown-out white area in the final image.

Category: How-To
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