GIMP — short for GNU Image Manipulation Program — is open source image editing software that makes it relatively easy to correct white balance.
How White Balance Effects Photos
Most light appears white to the human eye, but in reality, different types of light, such as sunlight and tungsten light, have slightly different colors, and digital cameras are sensitive to this. If a camera has its white balance set incorrectly for the type of light it is capturing, the resulting photo will have an unnatural color cast. You can see that in the warm yellow cast in the left-side photo above. The photo on the right is after the corrections that are explained below.
Should You Use RAW Format Photos?
Serious photographers will proclaim that you should always shoot in RAW format because you are able to easily change the white balance of a photo during processing. If you want the best photos possible, then RAW is the way to go. However, if you’re a less serious photographer, the additional steps in processing RAW format can be more complicated and time-consuming. When you shoot JPG images, your camera automatically handles many of these processing steps for you, such as sharpening and noise reduction.
Correct Color Cast With Pick Gray Tool
If you have got a photo with a color cast, then it will be perfect for this tutorial. While this technique may lead to more natural colors, it is possible that the exposure may suffer a little, so be prepared to make further corrections, such as using curves in GIMP. In the image to the left, you will see a dramatic change. There is still a slight color cast to the photo, however. We can make minor corrections to reduce this cast using the techniques that follow.
Adjust Color Balance
There is still a little bit of a red tinge to the colors in the previous photo, and this can be adjusted using the Color Balance and Hue-Saturation tools. Adjusting the color balance has made a minor improvement to the image. Next, we will adjust the Hue-Saturation for further color correction.
Adjust Hue-Saturation
The photo still has a slight red color cast, so we’ll use Hue-Saturation to make a minor correction. This technique should be used with some care as it can accentuate other color anomalies in a photo, and it may not work well in every case. In this photo, magenta saturation is set to -10, and the red saturation to -5. You should be able to see in the image how the slightly red color cast has been further reduced. The photo isn’t perfect, but these techniques can help you salvage a poor quality photo.
