Histogram basics
A histogram is a simplified display of the numbers of pixels at each of 256 brightness levels, producing an interesting mountain range effect. Digital SLR cameras, as well as many point-and-shoot models include histogram displays, which are charts on the LCD that show the number of tones being captured at each brightness level. Here, the non-SLR cameras have an advantage that is, the EVF and point-and-shoot models can display a real-time live histogram on the LCD as you compose an image and so you can then make immediate adjustments to optimize exposure. A DSLR, on the other hand, can’t show a preview image because the flip-up mirror gets in the way of the sensor prior to exposure, so histograms must be viewed afteryou’ve taken the picture. Each vertical line in the graph represents the number of pixels in the image for each brightness value, from 0 (black) on the left and 255 (white) on the right. The vertical axis measures that number of pixels at each level.
This image has fairly normal contrast, even though there are no true blacks showing in the histogram.
This low-contrast image has all the tones squished into one end of the gray scale.
A high-contrast image produces a histogram in which the tones are spread out.
Posted by Randy Norton
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Monday, September 28, 2009
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