Histogram

Is a graph of brightness. It ranges from black through grey to white along the horizontal axis, while values in the vertical axis represent the number of pixels at the appropriate brightness. It provides a means of checking the exposure of the image. If too many pixels are present at the left-hand side of the histogram, it?s likely that the image is underexposed, while if it?s weighted to the right, then it?s likely to be overexposed. A histogram function is built into some of the more sophisticated digicams, so you can instantly see whether the exposure needs adjusting by looking at the graph.