Digital cameras are versatile and can be set to automatically select the best settings for most situations to ensure the highest quality pictures are taken. In some cases, however, they may have trouble choosing the right white balance setting.
GIMP, short for GNU Image Manipulation Program, is an open source image editing software that makes it relatively easy to correct white balance.
- How White Balance Affects Photos
- Should you use RAW photos?
- Correct the color with the Gray Pick tool
- Adjust color balance
- Adjust Hue Saturation
How White Balance Affects Photos
Most light appears white to the human eye, but in fact different types of light, such as sunlight and tungsten light, have slightly different colors and digital cameras are sensitive to this.
If the camera’s white balance is not set correctly for the type of light being photographed, the resulting photo will have an unnatural color cast. You can see it in warm yellow in the left photo above. The photo on the right is after the corrections explained below.
Should you use RAW photos?
Serious photographers will say that you should always shoot in RAW because you can easily change the white balance of a photo while editing. If you want the best possible photos, RAW is the way to go.
However, if you’re a less serious photographer, the extra steps in RAW processing can be more complicated and time-consuming. When you create JPG images, your camera automatically performs many of these processing steps, such as sharpening and noise reduction.
Correct the color with the Gray Pick tool
If you have a photo with a color cast, it’s perfect for this tutorial.
Open the photo in GIMP.
Go to section colors † Levels to open the Levels dialog box.
Press the button Choose which looks like a pipette with a gray stem.
Click on the photo with the gray dot palette to determine that it is a medium gray shade. The Levels tool will then make automatic adjustments to the photo to improve the color and exposure of the photo.
If the result looks wrong, click the button Reset and try another part of the image.
If the colors look natural, press the button Okay †
While this method can result in more natural colors, there may be a slight decrease in exposure, so be prepared for further adjustments, such as using curves in GIMP.
The image on the left shows a dramatic change. However, there is still a slight tint in the photo. We can make minor repairs to reduce this throw using the following methods.
Adjust color balance
There is still a small shade of red in the colors in the previous photo, and this can be adjusted using the Color Balance and Hue Saturation tools.
Go to section colors † Color balance to open the Color Balance dialog box. You will see three radio buttons under Select Range to customize the title; this allows you to target different tonal ranges in your photo. Depending on your photo, you may not need to adjust all the shadows, midtones, and highlights.
Push button switch shadows †
Movement purple green slider slightly to the right. This reduces the amount of purple in the shadow areas of the photo, reducing the reddish cast. However, keep in mind that the amount of green will be increased, so be careful that your settings don’t replace one shade of color with another.
Adjust the cyan red slider in the midtones and highlights. Values used in this photo example:
Shadows: Magenta-Green 10
Midtones: Cyan-Red -5, Purple-Green 5
Key Features: Cyan-Red -6, Purple-Green 6
By adjusting the color balance, minor improvements were made to the image. We then adjust the saturation of the hue to further correct the color.
Adjust Hue Saturation
The photo still has a slight red tint, so we use Hue-Saturation to make a small adjustment. This technique should be used with some caution as it can bring out other color variations in the photo and may not always work properly.
Go to section colors † Hue saturation to open the Hue Saturation dialog box. The controls here can be used to affect all the colors in the photo equally, but in this case we just need to adjust red and magenta.
Click the radio button labeled m and move the slider Saturation left to decrease the amount of magenta in the photo.
Click the radio button labeled R to change the amount of red in the photo.
In this photo, Magenta Saturation is set to -19 and Red Saturation is set to -29. You should see in the image how the slightly red tint has been further reduced.
The photo isn’t perfect, but these methods can help you salvage a poor quality photo.