Digital photography provides us with a variety of tools to help make better photos. Unlike the old film days, we now have ways to review how well exposed or metered our shots are before actually printing them.
Most photographers contend with reviewing images on the back of the LCD screen to assess how well exposed they are. But because the LCD screens can be rather small and well illuminated, they can make photos appear better than what they actually look like on much larger computer screens.
Furthermore, sometimes viewing photos on the camera’s LCD screen might not show a loss of detail in the shadows or dark areas of an image, nor in the white or bright areas. When we’re really concerned about getting the best exposure for our photos, we might use the camera’s zoom-in feature to assess exposure and sharpness of our images. Additionally, we could use the Histogram tool of both our digital camera and image editor to see how well exposed our images are.
To some novice shooters, the Histogram may look like something a technician would use to see if your camera’s functioning properly. While the Histogram feature can be found in all 35mm digital cameras, the tool might not be easily visible; with some cameras you may have to push a button or two to bring it up. But that’s okay, once you learn how to interpret the Histogram, you might find it worth accessing and using a regular basis.
For this tutorial we’re going to primarily in Photoshop to understand how it works. The Histogram in a digital camera works nearly the same way it does in an image editor like Photoshop, so this tutorial also details how to read camera histogram.
What is the Histogram?
The Histogram is basically a graph showing the brightness distribution of an image with pure black on one end, pure white on the other and grey in the middle. Because measuring light is what photography is about, the Histogram works pretty well in a digital
camera, but it also may be a little confusing, so I’ll try to clarify with a few image examples.
Over-exposed Images
Many images we capture might tend to be over or under-exposed. It’s easy to tell when a shot is way overexposed because most of the detail in the image in blown out. In scenic images, a loss of detail often occurs with clouds and the sky in the background, such as with photo below. If you expose for the buildings, the background sky gets overexposed.
In the Histogram, the graph shows a bias to the right end. When the graph is bunched up against the right side (pure white), it indicates the areas of the image that are overexposed, or clipped – a technical term meaning a loss of detail or information in an image.
Underexposed Images
When the Histogram is bunched up toward the left (pure black), it indicates that areas of the photo are underexposed, and that details are clipped in dark and shadow areas.
Balanced Image
A more balance Histogram depicts a graph with the pixel representations spread across the graph and tapering off on both ends, such as in this image.
However, it’s often difficult to achieve a balanced graph for most photos. Significant contrast in the light, dark, and mid-tones in the foreground and background areas of a photo typically makes it difficult to get a balanced exposure.
In the first photo example above, it’s nearly impossible to expose for both the background and the foreground of the image.
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