Color Cast Photo Image Editing Tutorial

To try out the techniques covered here, you will need an image that has a color cast issue, which hopefully you won't. I've used a photo in which I deliberately set the white balance incorrectly to give the image a bluish tint.

When you've selected the image you want to work with, go to File > Open, navigate to your image and, after selecting it, click the Open button.

More experienced Adobe Photoshop users might consider using one of several techniques to approach the problem of color cast, including turning to the Hue/Saturation tool or Color Balance, but in Paint.NET, the Curves tool in RGB mode is what you will need to use.

Go to Adjustments > Curves and set the drop down to RGB if it's set to Luminosity. Because the color tint is blue I unchecked the the Red and Green checkboxes. This means that I will only be adjusting the blue channel of the photo. I clicked the blue line near the top right and then dragged it downwards a little. This has the effect of reducing the amount of blue in the image. Dragging it up above the diagonal line would increase the blue tint.

You can click on the curved lines in the Curves dialog many times to further change the shape of the curve and you will see the effects applied to the image. You should take care not to make extreme adjustments that will make the image look unnatural. You can right-click on a node to remove it.

I've added more nodes to the blue curve to increase the effect. The curve toward the bottom left represents the darkest pixels in the image and the top right represents the lightest pixels. This allows you to adjust different areas of the image differently. The curve in the accompanying image shows that the midtones have had more blue removed. Also, I've changed the curve for the light pixels to increase the effect on these.

At this point my image looks to have a bit of green tint along with the blue, so I've unchecked the Blue checkbox and checked the Green box so that I can make an adjustment to just the green channel.

I dragged the green curve down a little with a single node and have left it that at for now. I can always go back to it again and change it further.

The last channel for me to tweak is the red channel so I set the checkboxes correctly and increased the amount of red in the image by dragging the curve up above the diagonal. I also made a slight adjustment to the green curve, flattening it a little to give me a more pleasing result. When, like me, you're happy that you've got the best result you can at this point, click the OK button.

There are a few other adjustments that we can make to the image so don't feel that you have to make it absolutely perfect at this stage.

The next step calls for more Curves adjustment, but this time in Luminosity mode. Go to Adjustments > Curves and switch the drop down to Luminosity. In this mode, any adjustments that are made affect all the colors equally and just change the lightness and darkness of pixels across the tonal ranges. If you click on the thumbnail, you'll see that I applied a gentle 'S' shaped curve that has the effect of lightening the image overall and slightly increasing the contrast. When you're happy with your adjustments, click the OK button.

Another adjustment tool that could come in useful for you in this process is Brightness / Contrast. Go to Adjustments > Brightness / Contrast to open it and you can apply further changes by using the two sliders. I increased the Brightness by eight and the Contrast by sixteen. As with Curves, do take care not to make changes that are too extreme as the image will begin to look very unnatural.

This photo image editing tutorial should have given you the confidence to attempt to remove color cast from your images using the free pixel-based image editor Paint.NET, though do remember that sometimes the color cast can be too extreme to be corrected effectively.

Note: I mentioned earlier that blue and yellow are the two most common color casts. If you need to correct a yellow color cast, dragging the green and red curves downwards and the blue curve upwards should be a good starting point in most cases.