What is Frequency Separation and How Can It Improve Photo Retouching

Frequency separation is one of the most powerful techniques used in Photo Retouching and can be an invaluable asset to any professional looking to streamline their workflow. In this article, we’ll dive deep into these basics of frequency separation – discussing what it is and how to use it in Photoshop – so that by the end, you’ll have a better understanding of just how powerful (and necessary) this tool has become in the world of digital photography!

What is Frequency Separation?

Professionals commonly employ the Frequency Separation technique to achieve flawless skin in portrait images. This process eliminates blotchiness, redness, and skin discoloration while maintaining a natural appearance. While it applies to any skin area, it is primarily used for facial retouching.

The Frequency Separation process separates tones, colors, highlights, and shadows from the image’s texture. This allows you to retouch colors without affecting the texture or vice versa.

When analyzing images, it can be helpful to categorize the frequencies into high and low levels. High frequencies capture intricate details like hair, skin pores, and imperfections, while low frequencies convey volume information such as tonal transitions and lighting. By distinguishing these frequency levels, we can better understand an image’s components.

However, it’s important to note that while Frequency Separation preserves texture, excessive retouching can lead to an overly smooth and artificial look. Avoid the “porcelain face” effect by using this technique judiciously.

How to Use Frequency Separation in Photoshop

Frequency Separation is a powerful technique used in Photoshop for retouching and editing images. It involves separating an image into different frequency layers to work on details independently, such as texture and color. Here’s a step-by-step guide on how to use Frequency Separation in Photoshop.

Step 1: Duplicate the Image Layer Twice

You need to create multiple layers to separate the image into its tones and textures. Start by selecting the image/background layer and duplicating it twice.

For easier management, consider giving these duplicated layers more descriptive names. You can rename one as “Blur” for the tones and colors and the other as “Texture” for the texture layer. Remember to place the texture layer on top.

You can group the two new layers to enhance organization and facilitate comparison between the original and modified versions later on. Select both layers while holding the Control key (Windows) or Command key (Mac), then press Ctrl + G (Win) or Command + G (Mac) to create the new group. You can open the group using the arrow to keep the layers visible.

Step 2: Applying a Gaussian Blur to the Blur Layer

In this step, we will focus on adding a blur effect to the middle layer in the stack, known as the Blur layer. This layer contains the image’s various tones, colors, highlights, and shadows without any texture. We aim to smoothly remove the texture from this layer while preserving essential details.

Before we proceed with the blur, hiding the top layer is essential to observe the changes better. To do this, click the eye icon next to the Texture layer to turn it off. Once done, select the Blur layer.

Go to Filter > Blur > Gaussian Blur to add the desired blur effect.

In the Gaussian blur settings box, ensure the Preview option is checked. This will allow you to visualize the changes directly on your image. You can also click and drag within the preview box to focus on a specific area of the face.

Next, adjust the Radius slider to determine the intensity of the blur. It’s crucial to balance removing the texture and maintaining the subject’s clarity. Gradually slide the radius to the right until the texture disappears. In our example, approximately 2.0 pixels achieve the desired effect.

Once satisfied with the Radius setting, click OK to apply the blur.

Step 3: Adding Textures to the Texture Layer

To enhance the image with textures, we will add them on a separate layer. Start by enabling the visibility of the Texture layer by clicking the empty box to bring back the eye icon. Then, select the Texture layer.

Next, instruct Photoshop to remove the information from the blur layer and keep only the texture details. To do this, go to Image > Apply Image.

Make a few adjustments in the Apply Image dialogue box before clicking OK. Firstly, ensure that the information is subtracted from the layer where you applied the Gaussian blur. Select the Blur layer (or the name you assigned to the layer) from the Layer drop-down menu.

Next, change the Blending option to Subtract from the drop-down menu. On the right, you will see a Scale box. Set this to 2 and set the Offset to 128. Keep these settings consistent for any frequency separation you perform.

Once you have made these adjustments, click OK.

Step 4: Enhancing Texture with Linear Light Blend Mode

To restore the image’s texture, you need to change the Texture layer’s Blend Mode. Here’s how:

Make sure the Texture layer is still selected.
Go to the Layers panel and locate the drop-down menu next to Normal.
Choose Linear Light from the menu.

By adjusting the Blend Mode, the image will regain its original look. The visibility of the Group can be toggled off and on, and you’ll notice that the picture remains the same as the background layer. This is because all the information has been reintegrated while keeping them in separate layers.

4 Tips for Perfecting Frequency Separation

Creating two Frequency Separation layers is essential for precise, selective corrections. There is endless potential for the tools and techniques you can employ. The key is to determine which correction level is most effective for your specific needs beforehand. We will demonstrate practical ways to enhance your images using Photoshop Frequency Separation in the following examples.

Tip 1: Skin Softening

Achieving a soft and flawless skin effect in portrait post-production is highly desirable and often sought-after. However, the outcome can be disappointing and unrealistic when attempting to enhance an image without using Frequency Separation. Fine details, including the skin texture, tend to be lost, resulting in a “porcelain doll” effect.

To address this issue, Frequency Separation is a valuable tool. By focusing on the low-frequency layer and applying a Gaussian Blur filter strategically, the skin can be softened without sacrificing the essential details.

To accomplish this, begin by selecting a specific area of the face with the Lasso tool and setting a Feather between 10px and 20px. The Feather selection ensures a smooth transition between the softened and untouched regions.

Next, navigate to Filter -> Blur -> Gaussian Blur and adjust the value between 10px and 25px. You will notice that the skin becomes smoother and softer while retaining intricate details. This is because the low-frequency layer is being softened without affecting the high-frequency layer, which preserves the finer elements.

Tip 2: Skin Imperfection Removal

Discover an effective method for removing imperfections like blemishes from your skin using Frequency Separation. There are various ways to perform this type of retouching in Photoshop, but focusing on the correct frequency layer ensures a natural-looking outcome.

To effortlessly remove blemishes, we recommend utilizing the Patch tool. Access it through the Tools menu or by simply pressing the J key. This tool selects the undesired area and drags it to a nearby spot.

Choose a margin surrounding the blemish for optimal results and relocate it to an area with similar brightness. This allows Photoshop to calculate corrections accurately and achieve a consistent appearance.

Continue this process until your skin is as clear as desired. The blemishes will vanish while maintaining the intricate texture of your skin. Remember, alternative tools such as the clone stamp, spot healing, or healing brush can also be effective for blemish removal.

Tip 3: Highlighting Details in Photos

Frequency Separation can be used for more than just enhancing low frequencies. It’s also an excellent tool for highlighting essential details that may not be directly related to your skin.

One such detail that can significantly benefit from this technique is the eyes. When we look at a face, our attention is naturally drawn to the eyes – the same goes for portrait images. Since the eyes are a focal point, they must appear perfectly sharp.

There are various advanced techniques for emphasizing the sharpness of the eyes, but in this guide, we’ll show you a simple and effective method that works in most cases.

To begin, create a white mask in the low-frequency layer. Hold down the Alt (Windows) or Option (Mac) key and click “Add Layer Mask” in the layers panel. This will create a blank white mask without any adjustments.

With the white mask selected, choose a black brush with low hardness and an appropriate size for the area you want to enhance. In this case, we’ll focus on the eye.

Using the brush, apply strokes to the eye area. You’ll notice that the brush strokes remove opacity, making the eye appear brighter and more defined.

We’ve masked the low frequencies on the eye, allowing the high frequencies to stand out.

This technique is effective for enhancing eyes and works well for highlighting hair (especially when it’s in focus) and eyebrows. It’s perfect for glamor photography and any situation where the model’s features must be delicately emphasized.

Tip 4: Shadow Management

Sometimes, we can’t control light and shadows in the way we want due to lighting limitations. However, brightening the shadows in our base image would sacrifice detail and color quality. The solution lies in utilizing the divided frequency layers for maximum control.

Start by selecting the low-frequency layer. Then, choose the Dodge tool from the tools bar.

To achieve the best results, use a soft brush. Select Shadows in the Range drop-down menu and adjust the Exposure to around 15%.

Using the appropriate brush size for your retouching needs, lightly brush over the shadow areas you want to lighten.

You’ll notice that the shadows are effectively lifted without compromising the skin texture.

Remember, striking a balance and maintaining a clean and realistic result is essential. Avoid going overboard with the adjustments.

Frequency Separation is a beneficial retouching technique for photographers of any skill level. With its wide variety of applications, from fixing skin imperfections to brightening dull scenes, Frequency Separation provides a wealth of options for improving the look of photographs. Now that you know what Frequency Separation is and how it can be used to enhance photos, go out and try it in your work!

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