Think your photos might have a Color Cast» but you’re not quite sure? Use the Filter Pack in GIMP to check your photo.
The Filter Pack makes 6 copies of your photo. Each copy has a little color added to it. One has a little Green added to it, the next has Yellow added, another gets Red, the next gets Magenta, another gets Blue, and the last gets a little Cyan. These variations are displayed in a circle around the original.
When you add Yellow to Blue, they cancel each other out. Same with adding Green to Magenta. In fact, each of the colors has it’s opposite. (Red’s opposite is Cyan.) So here’s the cool part: If you have a digital photo with a Green color cast and you add a little Magenta, the color cast goes away.
When you look at the variations around your original they will each have a color cast. But if one of them looks more natural than the original, it means your original has a color cast, and the added color of the variation canceled it out. If you think something is off in your photo’s colors this is a great way to check.
This is also a useful trick when you know something’s off but you can’t tell what color is causing the problem. For example, a Red color cast can look very similar to a Magenta cast but adding Green (Magenta’s opposite) to a photo with a Red cast won’t fix the problem. Using the Filter Pack in this situation is a more organized way of figuring out the problem than adjusting sliders using Colors > Color Balance.
Ready to try out the Filter Pack? Here’s how:
1 Open your Photo in GIMP
I always duplicate the Background Layer first
Then duplicate the Background layer. Need to know how? Click here!» We want to make changes to the new layer, called Background Copy. Make sure it’s highlighted in blue.
Duplicating the Background layer is a good habit to get into when editing. In this tutorial, it’s especially important b/c we might need to adjust the opacity of the Background Copy layer later on.
2 Check the Variations
In the Main Window, go to Colors > Filter Pack. A window called Filter Pack Simulation will appear.
The Roughness slider controls how different the variations are from the original. Since we’re checking for a slight color cast it should be set quite low. Starting at 0.05 should do the trick.
Now, under the Windows heading, select Hue. Your variations will pop up in a new window called Hue Variations.
The original is in the center and the variations are around it. I can tell immediately that Red and Magenta variations make the photo look worse, not better. I see that Blue is too, well, blue, and so is Cyan. Yellow looks a bit too warm. On my monitor Green looks the most neutral.
Click on the variation that looks best to you. There’s no OK for this window. Just close it. Click OK in the Filter Pack Simulation window to apply the filter to your Background Copy layer.
*NOTE: Clicking on variations adds that filter without removing the last filter you added. If you click first on Green then on Red you’re adding both the Green and Red filters. If you need to reset to your original, exit the Hue Variations window and click Reset in the Filter Pack Simulation window.
3 Check your Work
Use the eye icon to toggle between the original (Background layer) and the color corrected image (Background Copy). How do I do that?»
Now that you can see your photo full size it may look like you’ve over corrected. This is where the opacity slider comes in handy. Just lower the opacity of the Background Copy layer a little. This will the make the corrections you’ve made seem less intense.
Check out the Before and After of my strawberry photo. The photo below is the Before. Roll over it with your mouse to see the After.
The Magenta color cast wasn’t obvious at first. Using the Filter Pack made it a lot easier to spot. Toggling between the Before and After makes the Magenta stand out that much more.
Are you a beauty or food blogger? Do you sell anything online? Getting color right for your readers is really important. What’s the point of swatching that new MAC lipstick if the colors don’t look the same in your photo as they do in real life? Accurate color will help make your food photos drool worthy too. In the next few posts I’ll be covering color basics from getting it right in camera, to correcting when you forgot, and even making the right choices for your online photos.
Stay tuned!
