Using “Levels Tool” in #GIMP

The Brightness-Contrast Tool may be the most commonly used tool in brightening and darkening pictures in GIMP. However, there are 2 other tools which are more powerful: the Levels and Curves tools.

Let’s see how the Levels tool (Figure 1) works.

Figure 1: Where to find the Levels Tool

The Levels tool has 2 sets of controls: Input Levels and Output Levels (Figure 2).  Input level shows a histogram representing the current brightness of the picture. The horizontal axis represents brightness while the vertical axis represents the number of pixels that have that brightness.

Figure 2: The Levels dialog with the Input Level and Ouput Level

To adjust the brightness or darkness of an image, all you need to do is play with the sliders (left-right):  shadow (darkest points in the image), midtone (a midpoint), and highlight (brightest points) (Figure 3).

Figure 3: Input Levels adjusted to brighten the image

While Input sliders let you expand the tonal range, the output sliders let you restrict the tonal range of the final image. Moving the leftmost output slider to the right means that nothing in the final image will be fully black, the parts that would have been black will now be a little bit dark and vice versa with the rightmost output slider.

Aside from the Input and Output Levels, you also have the option to use the Eyedropper buttons under the input sliders (Figure 4).  Just click on the left eyedropper button and then click on the darkest point in the image then do the same to match the right eyedropper to the lightest point in the image.

Figure 4: Adjusting the brightness using the Eyedropper button

And the last but not the least is the Auto button (Figure 5), found below the output sliders.  This is like other Auto levels in other photo editing programs. Once you click the Auto button, the image will automatically brighten. This may or may not be enough to attain the correct adjustment that you want but it also depends on the image. It is always worth a try.

Figure 5: Brightening the image with the Auto button

Important note:  Always have the “preview” checkbox selected so that you can view the adjustments as you edit it.

Next topic: Curves Tool

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2 Responses to “Using “Levels Tool” in #GIMP”

  1. Oooh! Nice, Ela! 🙂 Awesome. Tuloy mo pa mag-blog about GIMP!

    • itsmeela Says:

      Thanks Clair! Yup! Tuloy2x na to…After GIMP, I’ll try other programs naman. Probably Scribus or Inkscape. 🙂

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