Photoshop helps you with your photo bias

Neutral Ash is an important basis for correcting image bias.
How to correctly select the neutral gray reference point in the image, which has always been a difficult problem, I think in the actual operation to rely on in-depth theoretical understanding and a wealth of operational experience, I do not agree with the doctrine of the use of neutral gray theory. The following picture is in the use of digital cameras when the white balance set errors, you can use the neutral Ash method to easily correct the color, the neutral gray point of reference where to choose? Interested friends can have a try.