GIMP Exposure Tools

GIMP has a number of tools for image exposure manipulation. The ones that are relevant for photography can be found under the “Color” menu

histogramLevelsTool

Click with left mouse button on any of this page’s pictures to see it full size. Keyboard “Backspace” key brings you back to the exact page location.

There are two ways to open the “Levels” tool. The first one is through the top menu by selecting the “Colors” – “Levels” selections. The second method is a cascade of increasingly complex contrast brightness tools, starting with the “Colors” – “Brightness-Contrast” selection. I find the GIMP “Brightness-Contrast” tool rather crude, and mostly do not work with it, and skip directly to the “Levels” tool.

 

HistogramStartIn this example, when you look at the histogram, you see that there are no values on the bright side of the histogram. The brightness values from 207 to 255, which is the maximum brightness (pure white), have no data whatsoever. By moving the right hand slider to the first point on the histogram where there is actual data, you in fact stretch the whole histogram over the full range of available brightness settings. That is from Zero to 255. As you can see this has a significant effect on the image. The hair in the wig becomes more nuanced, the black just in front of the bust now has a bit more variation. Some dark grey is now discernible. The white styrofoam also has more definition or contrast.

The centre slider under the Levels tool histogram has a dramatic effect on the image. By sliding it left or right from its default value of 1, you either emphasize the bright colours (moving it left, or to higher values above 1) or dark colours (moving it right or to lower values below 1).

HistogramFavouringLightHistogramFavouringDark

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