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Using the Histogram |
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I'd be willing to bet that not many of you use the Histogram, know what it is, or what to use it for. Now you are going to find out. The histograms I am using here are from Photoshop, but Paint Shop Pro has a similar function. |
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The histogram is a graph. This one, and most of those I am using here, is a graph of luminosity values. A histogram can also graph the red, blue, or green values. The vertical axis of the graph represents the total number of pixels, the horizontal axis represents the pixel luminance value, with black (luminance value of 0) being on the far left and white (luminance value of 255) on the far right. Just from looking at this one, you can tell certain things. This image is not a dark image, as there is little information on the leftmost third. That is where shadows show on one of these. There is some very light or white color, the small spike near the right of the graph tells you that, but not a great deal of it. Most of the information in this image is contained in the center of the graph, so we can expect a normally balanced image with most of the detail in the mid color ranges. |
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Lets look at two more histograms: |
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OK. Now you can see what a Histogram does. So what? Well, lets go on to the contrast control and I'll show you what. |
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