Color Cast Correction

Color Sample Point.

The neutral sample points used to set the individual channel mid point tones are shown in the image below. I intentionally introduced a color cast into this sample image to better demonstrate the ability of curves to improve color cast.

This Color Cast correction removed Red (by increasing the Red channel’s mid point density value) and removed Yellow (by increasing the Blue channel’s mid point density value). The area sampled by Color Sample 2 was more neutral than that of Color Sampler 1. Remember that 0 is full black and 256 is full white. To increase density, you lower the RGB numbers. In some cases, you wont have a truly neutral area. To accommodate this, I set several color samplers in areas that are closest to neutral and average the reading as a place to start. Selecting an appropriate neutral mid tone value is the most important part of this process. It will take a bit of practice.

In most cases, you will need to adjust two of the three color channels. You generally move the two outlying numbers toward the middle value of the RGB numbers. For example, if your RGB numbers are R 145, B 139, and G 150, you would move the Blue channel midpoint until the Color Sampler in the Info platte reads 145. Then select the Green channel and move the mid point until it reads 145 on the color sampler info palette for your Color Sample Sometimes, (when two of the three RGB numbers are aligned—for example: R 120, B 114, G 120) you will only need to adjust one channel. In this example, you would move the Blue channel up to 120.

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