Remove a Color Cast

This is a beginner’s Photoshop how-to technique that will remove a color cast from an image. Any image that has too much red, green, blue, or yellow is said to have a color cast. 

You have a great picture but all of the faces are blue. Now panic sets in. How can you fix this! Take a deep breathe.

I will show you a simple two-step Photoshop how-to technique that will remove a color cast.

The Theory – Setting the Stage to Remove a Color Cast

Once the image with the color cast is opened you need to open the Levels dialog box – Image>Adjustments>Levels (Control+L).

If you are using a program other than Photoshop and can’t find a levels option, look for something called Histogram. Some software programs call Levels by its graphical name, Histogram.

The Levels dialog box has a graph of the image’s pixels. This graph is called a Histogram (Pixel Chart) and all of the image’s pixels, based on its value, are plotted in the graph.  The Histogram Pixel Chart is labeled as (A).

On the left side of the Histogram (Pixel Chart) are three eyedroppers.

The top eyedropper (B) is filled with ink and represents the shadow eyedropper.

The middle eyedropper is partially filled with ink and represents the midtone eyedropper.

The bottom eyedropper (C) is empty of ink and represents the highlight eyedropper.

On the bottom of the Histogram (Pixel Chart) are three triangles. These triangles represent the actual image shadow-midtone-highlight points.

The triangle on the bottom left (D) is filled with ink and represents the darkest shadow.

The triangle in the middle (E) represents the image midtone point.

The triangle on the bottom right (F) is empty of ink and represents the brightest highlight.

The Remove a Color Cast Process

This technique is going use the Levels eyedroppers to redefine the darkest pixel and brightest pixel and in the process remove a color cast by peeling the color cast from the image. 

Step 1: After opening the image,
Select, Image>Adjustments>Levels (Ctrl+L)

Step 2: Redefine the high-light point first

Select (click on it with the left mouse button) the highlight eyedropper and then click on the image where you think the brightest printable pixel (white) for that image resides.

In this example, I picked a place in the snow.

Step 3: Now select (click on it) the shadow eyedropper and then click on the image where you think the darkest printable pixel (black) for that image resides

You can try more than one place. Your last choice is what the eyedropper sets as the shadow point.

In this example, I picked a spot on a stocking cap.

The image might still need some color tuning and minor blemish repair but the color cast is gone 90% of the time.

What We Did to Remove a Color Cast– Geek Version

We used the Levels Highlight eyedropper to redefine our brightest white.

The eyedropper measured the color of the pixel we selected and determined what amount of color didn’t belong in the brightest highlight. Then the Levels Highlight option subtracted that amount from all the pixels in the image. Removing some/most of the cast and making the image brighter in the process.

Next, we used the Levels Shadow eyedropper to redefine our darkest black.

The eyedropper measured the color of the pixel we selected and determined what amount of color needed to be added to the pixel to make this pixel the darkest black. Then the Levels Shadow option added that amount to all the pixels in the image. Removing more of the cast and making the image contrast better in the process.

What We Did to remove a Color Cast – Non-Geek Version

We peeled off the color cast and made the image better by redefining the brightest and darkest pixels.

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