Post & Photo by Joe Farace Follow Joe on Twitter
Proper exposure of your in-camera monochrome image is important, especially for in-camera toned images because changes in exposure affect the density of colors (or lack of color) and overall style of the final image. How to obtain proper exposure is covered in lots of photography publications, such as The Kodak Most Basic Book of Digital Photography but in the meantime heres a quick review as it applies to monochrome image capture.
The latitude (the ability to over or underexpose) a photograph is greatest with color negative film. Slide film has the least amount of latitude, especially overexposure. Correct exposure is more critical for digital capture than film because digital sensors respond more like a hybrid of the two different kinds of film: Over exposure wipes out image data but the underexposure side of digital capture has more latitude. The downside of underexposure is the inevitable creation of digital noise, what you might see in a photograph that appears to be digital grain. As in all forms of photography, the secret to maximize digital image quality is to properly expose the image.
One way to critically evaluate exposure is by using the cameras built-in histogram function. A histogram is a graphical representation of a photographs exposure values from darkest shadows (left) to brightest highlights (right) and displays light values in 256 steps. Zero represents pure black and 255 is pure white or the classic Polar Bear in a Snowstorm. In the middle are mid-range values representing grays, browns, and greens. All of an images tones are captured when the graph rises from the bottom left corner then descends towards the bottom right. If it starts out too far in from either side or the slope appears cut off, then the file is missing data and the scenes contrast range may exceed the cameras capabilities. Tip: While the classic histogram features a bell-shaped (Gaussian) curve, not every photograph fits this distribution. Dramatic high or low-key images typically have lopsided histograms.
Joe Farace is the author of Creative digital Monochrome Effects from Lark Books. Its available in all the best bookstores as well as Amazon.com.