Color by Numbers 5 - Final judgement

Color Correction by the Numbers pt.5: The final judgement

The final word?

This is my fifth article on the subject color correction by the numbers. The previous four articles all centered around one task: make sure pixel (RGB) numbers agree with the colors in the image.

So, now that we have done our best to get these numbers right, the question is: does this finish our job of color correction (step 1 in the PPW)?

Surprisingly, my answer to that question is: no. No matter how unreliable our eyes are to assess color correctness, they get the final judgment. This may seem contradictory with previous statements I've made on this subject, but it's not.

Let me rephrase a proposition I made in the article Color by the Numbers compared with other methods: "People cannot trust their eyes to accurately judge color correctness."

Right now, I will rephrase this to the following:

"People cannot trust their eyes to accurately judge color correctness, but they can to judge color incorrectness."

When you think you have finished color correction, the numbers are good and your eyes tell you the photograph looks OK, then assume the work done and proceed with whatever other enhancements you want to make.

Winter scene

However, when the numbers are OK but your eyes tell you that the color is not good, then trust your eyes and keep working on the color. Ask yourself what is wrong. Is it the whole image or just part of it? Only the dark tones or only the light tones? Is one color offensive? 

Maybe the curves need finetuning. Maybe the layer needs a mask. Reduce the layer opacity and judge if that improves or worsens the colors. Maybe you need to duplicate the adjustment to make the correction even stronger.

The final example

I have an example image, see figure 1. This is a photograph as the camera delivered it (apart from some cropping), shot in Auto-WB. Quick analysis shows that the image is too blue. Snow is supposed to be white, so it should be easy to correct. See figure 2 for a corrected version that makes the snow neutral.

Figure 1. Original image

Figure 2. Corrected for the snow

Now how does that look?

If you ask me, figure 2 looks more like an autumn scene than like a winter scene. The photograph has gotten a brownish muddy look. While removing the blue cast, we have also removed the coldness that is distinctive for winter scenes. Even though the colors are technically correct, aesthetically they are not. I simply reduced opacity to taste (60%) and arrived at figure 3.

Figure 3. My favorite hue

Figure 4. PPW applied to fig.3

For completeness, and to show that the "cast" does not blow up, I have finished the PPW for this picture. The final result is figure 4. I think it looks good, and the blue in the snow has not become objectionable.

You can think of other examples. An interior illuminated by candle light may lose its mood when we force the white table-cloth to be absolutely neutral. Remove the warm orange glow from a sunset image and you lose its essence.

Numbers are the best help to find and tackle a color cast, but they don't have the final word. Only when our eyes and taste agree with the numbers, then they are correct.

Gerald Bakker, 16 March 2015 / 11 Feb. 2016

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