Photoshop color balance: independent adjustment of different colors (below)

We know that the operation to increase the red component, in other words, is to increase the red light level. This is easily felt in the curve operation. The same is true for green and blue. Upgrading these three primary colors will increase the overall brightness of the image. At the bottom of the color balance setting box there is an option to "hold the brightness". Its function is to decrease the brightness when the three primary colors increase, and increase the brightness when the three primary colors decrease, thereby offsetting the brightness changes caused by the increase or decrease of the three primary colors. As shown in the following 4 pictures, the first two pictures are the effect of closing and opening the maintain brightness option when the middle tone is +100. The last two are midtones -100, the effect of turning off and on the keep brightness option.

Source: Computer News