How can I adjust skin tones accurately in Photoshop if I have color vision deficiency?

Question

I have a color vision deficiency and find it hard to judge whether skin tones look natural when editing in Photoshop. Are there tools or methods I can use that rely less on visual judgment, such as numeric values, sampling, or reference targets, to correct skin color more accurately?

user37321 · Answer

I think I found something interesting. It feels like a revelation to me!

There are some articles about using the eyedropper but on CMYK model.

I found a very, very simple method that I feel works well to adjust skin colors on RGB model. I am currently testing on Caucasic skins, but I feel it works for almost all skin tones.

Open your color panel and use RGB sliders.
Grab your eyedropper and take some measures of the skin.
The trick is that the 3 sliders need to form (more or less) a straight line. That is it!

Another thing to consider is that this 3 sliders should stay below this 45° angle with respect to the vertical if it is outside this the skin will look too saturated.

Some Initial tests

Here is a photo that has a very clear yellow-green tone:

Taking some random samples the RGB sliders are out of my (currently arbitrary) graph.

Instead of removing the green, I opted to slide up the blue channel, because I noticed the lack of this.

It is not perfect but a big improvement.

One thing I noticed. This relation is more or less stable. The problem with specific measures, instead of proportions is that it is difficult to know what part to measure, highlights, shadows, etc.

With this method, you can measure with some freedom. It only will move your sliders left and right, will make it more or less vertical (depending on the style of the photo, saturated or not very much saturation)

Also, this gives me the freedom to choose which channel to adjust. The obvious choice on the example was to reduce the green, but It is not that important and moving the blue worked.

You now can reduce the brightness, reduce the saturation or do some other adjustments. The proportion of the 3 channels is what is important.

I think this is a good starting point.

Photoshop is lacking an important tool

In video editing, one important thing is to keep consistent skin tones. Some professional programs have a vectorscope. It is a type of graph to view color values (think of it as another type of histogram). There is a line called the skin tone line. https://www.google.com/search?q=vectorscope+skin+tone

Let me simulate this using an oldie free plugin.

This is a mapping of the values of the pixels on the white square on a 3D cube viewed from above. This is similar to the vectorscope.

On the original image, we see the pixels a little closer to the yellow axis.

Now compare it to the corrected image, where the same zone is mapped around the middle ground between red and yellow: Orange.

It is a little closer to the center too because we added blue, but that is not important.

According to videographers, this line is independent of skin tone (race) it can be closer or further away from the center but stays on the same hue (polar) angle. This means the same of my findings. The proportions of the colors are what matters.

This is a tool that would be handy in Photoshop.

Mvs Color cube plugin. It only works on old versions of photoshop. Probably 32 bits. http://www.vicanek.de/imageprocessing/colorcube.htm