Smoothing Skin and Surfaces with the Frequency Separation Technique

Seriously, the “Frequency Separation Technique”? When I read terms like that, I become increasingly convinced that professional Photoshop retouching is in a league of its own. The good news is that you just need Evernote (or some other note taking app) to track a few of these tricks until they become deeply ingrained. This is one worth knowing.

This particular technique requires just a few steps in Photoshop using duplicate layers and layer blending modes (that’s common enough) but it also uses an obscure option called “Apply Image”. What makes it so interesting is that you get to separate the colour of a layer from its texture so you can apply transformations to them separately (or add a layer in between to impact tonality).

Photo by VonWong Photography

Here’s an explanation by retoucher Ben Secret for his tutorial “Retouch images with frequency separation” as summarized by PetaPixel in a post they did on the subject last November:

[Frequency separation is] a technique that enables you to selectively process not only different areas of an image, but also different detail levels. Frequency separation involves creating a high detail (high spatial frequency) layer and a low detail layer from a source image [...] Using this technique enables you to smooth and rework rough and fine details independently, and opens up some very high-quality and non-destructive methods with which to sharpen your images.

Frequency Separation in Action

I was only just made aware of this technique today after reading a blog post by Benjamin Von Wong in which he creates some stunning shots at the Disney Concert Hall in LA where professional photography happens to be prohibited. He does the shoot guerrilla style as he sneaks in a battery-powered strobe for extra lighting. He then uses Photoshop to remove distractions and takes the photo to another level with Frequency Separation. It created a great look for what he was trying to achieve which was a sleek group shot for the classical music group Trio Dinicu.

Before going any further, have a look at some interactive before and after images posted by Julia Kuzmenko McKim. Once you see those, you’ll want to learn more about this technique.

Below is Von Wong’s video about the image above. Many other details can be found in the related blog post.

Summary of Steps

Take note of these steps (edited from Von Wong’s own summary):

• Step 1: Duplicate your image layer twice, call one “Tone” and the other “Texture” (put texture above and hide it for now)
• Step 2: Select the “tone” layer and apply a Gaussian Blur. The value you choose for the blur actually defines how much detail will fall into the “tone” layer and how much falls into the “texture” layer. Sara Kiesling, in the video below, blurs until the colours start to overlap.
• Step 3: Now reveal and select the “texture” layer. Go to the “Image” menu and select “Apply Image”. The dialog prompts for a layer, so choose the “tone” layer from Step 2. Then pick “Subtract” for the blending mode and set a “scale” value of 2 and an “offset” value of 128 (don’t ask why). Give this layer a blending mode of “Linear Light” from the layers palette. The two layers combined are now IDENTICAL to your original!
• Step 4: You can now paint a on a new layer between the two you created to smooth things out… or clone/heal/patch directly on the “texture” layer. Cloning in the “tone” layer is good for smoothing out highlights and redness on skin. Make sure that when you clone or heal that your brush is set onto “current layer” (this is critical). The key is to play around.

Skin Retouching with Frequency Separation

Sara Kiesling‘s video is referenced by Von Wong in his post and it’s a must-watch as well as she shows you exactly how she uses this technique to retouch skin. She also shows a dodge and burn technique and how to apply some virtual makeup:

As noted by Fstoppers, fashion and beauty photographer Elena Jasic has also created a full 15-minute video to show exactly how she uses this technique for high end skin retouching.

I’ve tried this on a photo and it works amazingly well. I’ll post-process one photo fully and add it here soon. If you try it out, let me know and share the before/after results.

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