Tuesday, January 30, 2007
The Magic Of Histograms
Learn to read your camera's histograms and get the best exposures possible for your subject
Labels: Learning Center
The histogram sometimes looks a little intimidating. It was never part of film photography, and it certainly doesn't look very creative. It's a graph based on mathematics, but to use it, you don't have to know anything about math. This article will give you an overview of what to look for in your histogram and offer some specific photographic examples showing both an image and its histogram.
While the histogram looks rather technical at first, the basics of reading it are fairly simple. Camera manufacturers haven't always made finding the feature in the menus that easy, so check your camera's manual to see how to turn it on, if your model includes it.
With digital SLRs and many digital cameras, you have to look at the histogram after you take the shot. With some digital cameras, you can turn on the histogram for live viewing as you prepare to take the picture, which can be helpful in adjusting exposure on the fly.
The histogram is a chart that looks like a hill, mountain range or multiple hills, but the key elements are the slopes at the left and right. Some histograms are solid graphs, while some just show a line where the tops of the points are-both are identical in use, only different displays.
To read exposure, begin by looking at the left and right parts of the chart. The left shows the darkest parts of the scene and the right displays the highlights. The entire width of the graph represents the total range of tones that your sensor can capture. Anything beyond the left edge is pure black, outside of the range of the sensor, so nothing is recorded in those shadows. Anything beyond the right edge is pure white, and again, outside of the range of the sensor.
A satisfactory exposure will have a full range of tones from left to right appropriate to the scene. There's no "right" shape to the histogram, since that will change depending on the types of tonalities in your scene. The key, though, is to be sure no exposure information is clipped at the right or left (the graph is abruptly cut off), which represents the exposure level where detail is gone. A cutoff or clipped histogram means details aren't being captured at all.
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