Sometimes an image won't have the correct color balance. This can occur for many reasons. It may not have been shot with the correct white balance in the camera, or it may have been shot low in the sky and affected by atmospheric reddening.

Setting the White Point defines white in the image and can also increases the contrast. In many cases it can go a long way to correcting the color in the image.

Below we have an image of Jupiter that was recorded with the wrong white balance. This made the color incorrect. The image is also low in contrast because it was somewhat underexposed and not all of the available dynamic range is being used.

Figure 1 - Jupiter and Europa with incorrect color shot with the wrong white balance. Hold your mouse cursor over the image to see a comparison between the original image and the corrected image.

We set the white point by using the Levels command in Photoshop.

• Under the Image pull-down menu, select Adjustments > Levels. The Levels dialog box will open (Figure 2).

Figure 2 - Photoshop's Levels dialog box.

We can adjust the white point for the entire image's combined RGB channels by dragging the white point slider to the left. This will increase the contrast, but it won't correct the white balance (Figure 3).

Figure 3 - The white point adjusted in the combined RGB channel. The contrast is increased, but the color is still wrong.

Instead, what we need to do is adjust the white point in the individual red, green and blue color channels.

Figure 4 - Adjusting the white point in the individual color channels.

• In the Levels dialog, pull down the red channel first under Channel (Figure 4, Number 1).

• Drag the white point slider in the red channel to the left until it almost reaches where the histogram begins. Leave a little bit of headroom Figure 4, Number 2).

• Now pull down the green channel under Channel.

• Drag the white point slider in the green channel to the left until it almost reaches where the histogram begins. Leave a little bit of headroom.

• Finally, pull down the blue channel under Channel.

• Drag the white point slider in the blue channel to the left until it almost reaches where the histogram begins. Leave a little bit of headroom.

We have now adjusted the white point in the image and corrected the color balance and increased the contrast at the same time (Figure 5).

Figure 5 - The white point adjusted in the combined RGB channel. The color balance is corrected and the contrast is increased. Hold your mouse cursor over the image to see a comparison between the original image and the corrected image.

Photoshop's Auto Color

Instead of adjusting the white point in each individual color channel, you can try using Photoshop's auto color correction commands. They don't always work, but it's easy to try them and it can save some time.

• In the Levels dialog, click on the Options button (Figure 6, Number 1). The Auto Color dialog box will open.

Figure 6 - Photoshop's Levels and Auto Color Correction dialog boxes.

• First thing is to change the Shadows and Highlights Clip Points from their defaults to 0.01% for both (Figure 6, Number 2 and 3). This will prevent gross clipping of the highlights and shadows. Be sure to check on "Save as Defaults" at the bottom of the Auto Color Correction Options dialog box.

• Under Algorithms try each one to see which produces the best results (Figure 6, Number 4).

For this particular image, Find Dark and Light Colors with Snap Neutral Midtones produced the best result, nearly identical to adjusting the white point slider in each individual color channel.