Motivation: Colorcast corrections are a frequent problem
Features: Shadows, lamps even the sun have their not always welcome colorcasts

Despite some of the most sophisticated programs and settings in digital SLRs (my Canon Rebel has 6 exposure settings devoted to special lighting conditions), getting the color balance right on digital shots is difficult. Part of the problem is that you and I are built with lying eyes. It appears that evolution has found it advantageous to allow your eyes and brain to pre-fill flash shadowed areas and temper various colorcasts closer to the "true", underlying colors then condition should allow.

Thus shadowed areas in digital images appear more cool and blue then we remember. Or beach shots appear like bleach shots. Or full days sun appears a bit more garish than even we thought it looked like. So more often than not digital photographers want to make some colorcast corrections. Hence our tale about before and after.

Here is Bern Switzerland before:


And here is Bern Switzerland after:

The problem at Bern-before is that the shadowed areas below the setting sun appear to be tinged blue and darker than what was originally perceived. This occurs all the time in landscape photos. So our mission is to do a colorcast correction.

Now what takes this correction beyond most simple photo editors (and many photo album programs have just such editors), is the need to mask off the lower portion of the scene while leaving the town and buildings out of the mask. If you apply corrections to all of the image the sky and building just wash out. So we must use a professional editor like Corel PaintShop Pro or Adobe Photoshop Elements. In fact we will start with the easiest and fastest solution in showing 5 possible colorcast corrections.

PaintShop Pro: Manual Color Correction

One of the fastest and easiest solutions is to use the Manual Color Correction tool. Unfortunately, in Paint Shop X, this versatile command has been inexplicably demoted from the Adjust Menu. You have to restore it. Right click on the menu or toolbar, and choose Customize and then the Commands tab. In the left Categories pane choose the Unused Commands. The right pane will change and fill up with all the resources in PaintShop Pro that you thought were gone. Scroll down to the Manual Color Correction command. then just drag and drop the icon on to the toolbar or into the Adjust menu (or both). Voila one of the most useful Color correction tools is restored.

Now first mask off the area which is deeply blue tinged in the image using the Freehand selection tool. Be sure to have a feather of about 20-40 pixels in the properties bar before you do the masking. Remember that in PaintShop Pro the full mask extends to where you do the trace (the aqua line as you draw the mask). The feathering extends beyond this trace edge 30 pixels or whatever feather size you set. This feathering will allow blending of the effect gradually and hence will not leave a high contrast border at the mask edge.

Now click the Manual Color Correction command - and it will only be applied to the masked off or selected area of the image. Click the Manual target color radio button and then set the color to white just as in the screenshot. What this means is that PaintShop pro will correct the color of any area you mark in the Before: thumbnail. It will change the bluish tinge to be white. You can see in the After: thumbnail the color has been moved to white. And in fact the bluish colorcast has been removed from all of the masked off area. We are done.

In fact, I have found the Manual Color Correction to be so good it reduces my color corrections times by at least half and I know now that I can handle even the meanest color correction problems. The Bern Switzerland after image is from using this tool along with a little HSL color warming.

Adobe Photoshop: Two Methods

Photoshop also has a one step solution to colorcast using the Levels dialog. However, there is a masking problem with Photoshop that effects this method. The problem is that when you feather with Photoshop masking tools the feather is applied to the inside of the masking trace. This has the effect of rounding the corners and making it necessary to apply a second mask with 0 px along the outside borders of the image. See here for a tutorial on the problem.

However once the area is masked - all you have to do is choose Image | Adjustments | levels in Photoshop. When the dialog pops up choose the third ink dropper in the bottom right corner (it has white ink in its icon). Then select an area in the image that should be white and click the dropper there. If you have clicked the Preview option, the corrected image will appear somewhat as shown in the above screenshot. I say somewhat because the actual correction is too contrasty. The screenshot above is after adjusting the Input White Level value in the Levels dialog. This technique reduces the contrast.

The second Photoshop technique for color correction reduces contrast but requires two steps.

In this second method we use a combination of the Image | Adjustments | Channel Mixer and the Image | Adjustments | Curves commands to correct for colorcast with notably less contrast in the results. Using the Channel Mixer dialog with the Output Channel set to blue we can reduce the blue tinge. Then use the Image | Adjustments | Curves command to reduce the shadow darkness.

But on this step, use the color dropper tool first . The Curves dialog like the Levels dialog, has 3 eye droppers in the lower right corner. Again choose the third or white dropper and then click on an area under the mask that should be pure white. Again, the shadow will largely be removed. Users may need to make some small additional adjustments - as I have done here with the pencil in the Curves dialog. If you compare the trees under the dialog box with those in the previous screenshot there is less contrast and less blue tinge. Now some argue a hint of blue tinge should be left in - hence two methods.

Classic Method - RGB and Brightness Contrast Iterations

Some users will not have the special Curves, Levels, or Manual Color Correction tools available in Photoshop and PaintShop Pro. So our last correction method uses the classic technique using the RGB and Brightness/Contrast tools available with most photo edit programs.

I usually do this in small increments starting with the Brightness Contrast tool first. I up the brightness by about ten percent and reduce the contrast by similar or less amount. Then I make a larger adjustment to the RGB values. Notice that I am increasing all of the values - just consistently less for Blue. This increases the brightness of the overall masked area but also shifts from blue to light yellow tone. Since I am doing two or three iterations, I also remove the mask in those areas where the correction looks good enough. The process is longer; but also affords users more precise control on the overall results.

Summary

So here are five methods for reducing the colorcast in your images. Obviously, the newer more powerful photo editors provide potent colorcast correction tools as in the case of PaintShop Pro's Manual Color Correction. However, even these tools can be defeated by deep colorcasts where the shift is 3 stops or more. In the process of removing the offending hue - nearly all color is removed and speckling occurs. Users might want to consider changing the image to grayscale and then adding back just a touch of color. In the meantime feel less intimidated by colorcasts with these color correction techniques in your toolkit.