How to use frequency separation in Photoshop

Frequency separation In Photoshop, the finer picture editing is achieved by separating the skin texture from the color light and dark. The specific steps are as follows: 1. Copy the layers and name them separately, one layer retains the details, and the other layer applies Gaussian blur (radius 8~15 pixels); 2. Use the "calculation" function to merge the two layers to generate high-frequency parts, and set the blending mode to "linear light"; 3. Adjust the skin color in the low-frequency layer, and repair the details in the high-frequency layer without interfering with each other; 4. If the skin is gray, check whether the blending mode, color adjustment position and blur parameters are reasonable. After mastering this technology, the photo editing effect is more natural and controllable.

It is actually not difficult to use Photoshop to perform frequency separation, the key is to understand what it does. Simply put, frequency separation means separating the texture (such as pores, fine lines) on the skin from the color and light and dark, so that the skin can not only adjust the skin tone when editing pictures without making the skin look fake. Next, I will explain how to operate it in steps.

Preparation: Copy the layer and Gaussian blur

Before starting, copy the portrait layer to two layers, name it "high and low frequency" or similar names for easy identification. Next:

• One layer preserves details without making any changes;
• The other layer is made of Gaussian blur, and the degree of blur is based on the invisible pores and small defects. The radius is generally set at about 8 to 15 pixels , depending on the size of the picture.

The key to this step is to be blurred enough, but not to cover up the structure of the entire face. If the blur is too heavy, it will be difficult to adjust later; if it is too light, it will not achieve the separation effect.

Separate high and low frequencies: apply calculation commands

Next, go to the core step and use the "Computation" function to merge the two layers into a difference layer:

1. Open "Image → Calculation" in the menu bar and select:
   • Source 1 is the original layer
   • Source 2 is the layer you just blurred
   • Select "Difference" in the mixed mode
   • Select "New Document" as a result

This newly generated document is the high-frequency part, which is where you want to deal with the skin texture. Drag it back to the original image and set the blending mode to "Linear Light".

At this time, you will see the picture brightening or even a little strange. Don’t worry, this is normal, because the high and low frequencies have been successfully separated.

Treat high and low frequencies separately: adjust the skin tone first and then repair the texture

Now you have three layers:

• At the bottom is the blurred low frequency layer (used to adjust the skin tone)
• The middle is the high frequency layer (used to repair details)
• The top is the original layer (can be temporarily closed)

Handling low frequency layers:

• Adjust skin tone with curves or color levels
• You can also use a soft edge brush to brighten/dark it

Handle high frequency layers:

• Use the imitation stamp tool to gently remove acne and spots
• Be careful not to have too high transparency of the brush (recommended to be less than 30%)
• Don't over-spray, otherwise it will appear unnatural

These two parts are processed separately and do not affect each other. This is the advantage of frequency separation.

FAQ: Why does the skin turn gray after repair?

Many people find that the skin tone is not right after the frequency separation, which is usually the following reasons:

• The high frequency layer uses the wrong hybrid mode
• Color adjustment only works on one frequency layer
• Gaussian fuzzy parameters are inappropriate, resulting in separation failure

The solution is also very simple:

• Ensure that the high frequency layer is in "linear light" mode
• Color adjustments are made in the low frequency layer, and the high frequency layer only needs to repair details
• Go back and check if the Gaussian fuzziness is reasonable

Basically that's it. Frequency separation sounds advanced, but in fact, as long as the steps are correct, you can master it by practicing a few more times. It may feel troublesome at first, but once you become proficient, you will find that it is much easier to control than direct skinning, especially suitable for later commercial portraits.

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