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Histogramm feature of PhotoPerfect

The histograms in PhotoPerfect are diagrams which show the distribution of the brightness values (tone values) of an image using finely stepped columns which give the appearance of a complete curve (there are 256 values for an 8 bit image). Each brightness value corresponds with one column. All columns together produces what is known as the tone value curve. The X-axis of the diagram shows the range of brightness, with black to the left and white to the right. The Y-values give the number of pixels of the given brightness within the image.

If an image is correctly exposed, the histogram will have brightness values across the whole range from 0 to 255. If it is underexposed there will be more tone values in the dark range and hardly any in the right range (e.g. values from 0 to 200). An overexposed image, on the other hand, will have values in the upper range, e.g. 50 to 255.

By selectively manipulating the histogram, i.e. the values of which it consists, it is possible to influence the color channels red (1), green (2) and blue (3) as well as the brightness channel (4) for the whole image. In other words, you can influence both the total brightness as well as the brightness of individual channels.


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