Back in the old days of film, a photographer could choose from various emulsions
to achieve a specific look for an image. Kodachrome was the standard by which all others were judged for years; its accuracy was unparalleled. Velvia, the supersaturated Wichita Falls Photo
transparency film, is a favorite of mine, though it’s too saturated for some. I always thought it replicated how your memory remembered the scene, slightly exaggerated across its palette.
With digital technology, we now have the ability to “dial in” the contrast and saturation we require. This, too, is a function of the algorithms in the software.
The histogram is another powerful informational tool of the digital realm. It displays the distribution of tones in the digital image and resembles a cross-section of a mountain range. It can be displayed on your camera monitor, either separately or superimposed over the image just shot. The breadth of the range the histogram displays, from left to right, represents 256 levels of brightness—from pure black at 0 to pure white at 255. The “mountain peaks” tell you the number of pixels that are being used, or
stacked, in that particular brightness level. The higher the peak, the more saturated that color or tone.
It’s impossible to say that a perfect or normal histogram can exist, as the tones used depend on what you are trying to accomplish
in your photograph. A histogram heavily 49
weighted to the left, toward black, could, for example, appear for an image of a bow wave of a ship, the dark water and light wave tops each being correctly exposed. On the other hand, an Arctic explorer’s face in the snow could be heavily peaked toward the right, the bright end of things. Often you’ll have to decide whether the image works, regardless of what the histogram tells you.
As a camera setting, the histogram can be displayed immediately after shooting a photo, or it can be called up on the monitor via menu or button pushes.
The image on the next page is a good example of not reading the histogram literally. The wave in the image is lit well, and the background appears as it should. This image would not produce a “classic” histogram of the evenly spaced mountain range. Again, the histogram is information, not creative genius. As a tool, the histogram will tell you, with a fairly straightforward image, if the exposure is
over or under, by indicating the location of the peak of the range. Adjustment to the exposure can be made at that point.
When you’ve gone into Photoshop and made Level or Curves corrections, the histogram displayed will be more evenly distributed.
Using the histogram’s power, the photographer can check the exposure immediately to determine whether the photo is within the range the chip can handle.
You’ll often see “blinkies” in one form of
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the histogram—that is, a warning that the camera senses an overexposed area. This will literally appear as a small patch of white, overexposed area blinking to black on your camera monitor. The blinkies tell you that the chip cannot hold any detail in the blinking area when viewed or printed. Personally, I don’t give the blinkies much attention, because I like to concentrate on the image at hand.
However, if you are photographing a static scene, and not an event, this warning can be of tremendous benefit, as lighting and exposure can be adjusted or changed to eliminate the overexposed area.