How to improve contrast using GIMP

Before contrast mask: the face and flowers are too dark; the sky is too bright.

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By Two Hands Gatlin
eHow Community Member

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Contrast masking is a way to compress the brightness range and get good detail in both highlights and shadows. The result is similar to HDR processing, but uses only one image and covers a more limited range of brightness. If the highlight or shadow detail is not available in the original image, it can’t be brought out with this method. In that case, real HDR, using multiple images, might be required.

This process will work in most photo editors, using slightly different menus and controls. This tutorial gives general directions for each step, followed by specific mouse-click directions for the GIMP photo editor.

GIMP is free - you can download the Windows version at http://sourceforge.net/projects/gimp-win/

Difficulty: Moderately Easy

Instructions

Things You'll Need:

A digital photo
Photo editing software. (This article is geared toward GIMP, but the same steps are available in most photo editors. The menus and names may be different.)

Step 1

Duplicate the layer:
Right-click on the background layer and select Layer –> Duplicate
Step 2

Desaturate the layer you just created:
Right-click on the new layer, then Colors –> Desaturate
Step 3

Invert the layer you just created:
Right-click on the new layer, then Colors –> Invert
You should now have what looks like a black & white negative of the image.
Step 4

Set the new layer’s blending mode to Overlay:
In the layers dialog window, select Mode –> Overlay
Step 5

Apply a Gaussian Blur:
Right-click the image window, and then Filters –> Blur –> Gaussian Blur
Adjust the radius until it looks the way you want.
Step 6

Adjust the Opacity of the layer until it looks good:
Use the slider at the top of the Layers window.
Step 7

The face and flower beds have good exposure, and the sky is darker, although it could maybe be darkened a little more.