Three techniques of restoration: three techniques of restoring portraits in the later period.

1, Photoshop hyperbolic hand grinding retouching method. Hyperbola uses the mixed mode of layers to remove color, which reduces the brightness of the image and produces difference contrast. As an observer, it can show the defects and unevenness on the skin, and it can also truly reflect the light and shadow, so that people can clearly see the problems that need to be solved in the film. Then, the deepening and shallowing of the curve adjustment layer is actually a repair action on the mask with a white brush, which brightens the dark pixels and darkens the bright pixels to smooth the concave-convex surface without destroying the details and quality of the original image, thus creating a lossless retouching.

2.Photoshop neutral gray manual polishing retouching method. Neutral gray retouching is an extension of hyperbola retouching, and the effect is better. However, the difference between this method and hyperbola retouching is that the color needs to be adjusted or recolored after retouching to get a complete and good effect.

3. Photoshop high and low frequency stripping method. High and low frequency crust is completely different from hyperbola and neutral ash, and its function is only crust. Of course, it also improves aging to some extent. It is a combination of Gaussian blur and Gao Fancha retention filter, and can also be understood as the form of anti-Gao Fancha retention.