What is frequency separation?
One of the most utilized techniques in portrait retouching is the act of frequency separation. Frequency separation allows you to split an image into what are called frequencies. There are two of them – a high frequency, which contains the texture information, and a low frequency, which contains the color and tone information.
Notice in Figure 12.11 that there is a texture layer over the light red square. This is exactly how a texture works when applied to a photo. So, instead of adding a texture layer that’s applied over a layer, think of frequency separation as extracting the texture from a photo and separating the photo and the texture:
Figure 12.11 – The theory of frequencies – high is texture, low is tone and color
In the following sections, we will dive into the more practical uses of this theory, as well as complete a project to show the concept in practice.
