Here's a step-by-step guide to frequency separation in Photoshop:
1. Duplicate the Layer:
* Open your portrait image in Photoshop.
* Press Ctrl/Cmd + J twice to duplicate the background layer two times. You should now have three layers: "Background," "Layer 1" and "Layer 2".
2. Rename the Layers:
* Double-click on "Layer 2" and rename it to "High Frequency" (HF).
* Double-click on "Layer 1" and rename it to "Low Frequency" (LF).
* The Background layer can remain as it is.
* Make sure the layers are in this order from top to bottom: HF, LF, Background.
3. Blur the Low Frequency Layer:
* Hide the High Frequency layer (click the eye icon next to the layer).
* Select the Low Frequency layer.
* Go to Filter > Blur > Gaussian Blur.
* Adjust the Radius slider until the skin details like pores and fine lines start to disappear, but you can still see the overall shapes and tones. You're essentially blurring away the fine details. The precise value depends on the image resolution and the desired result. A common starting point is between 4-8 pixels, but you may need more or less. Click OK.
4. Apply Image to the High Frequency Layer:
* Unhide the High Frequency layer (click the eye icon).
* Make sure the High Frequency layer is selected.
* Go to Image > Apply Image.
* In the Apply Image dialog box:
* Layer: Choose Low Frequency (or the name you gave to the blurred layer).
* Blending: Choose Subtract.
* Scale: Enter 2.
* Offset: Enter 128.
* Invert: Ensure it's NOT checked.
* Click OK.
5. Change the Blending Mode of the High Frequency Layer:
* Make sure the High Frequency layer is selected.
* In the Layers panel, change the Blending Mode from "Normal" to "Linear Light".
You have now successfully separated the frequencies!
Retouching Workflow:
Now you can start retouching using the frequency separated layers. Here's how:
* Low Frequency (Color/Tone):
* Select the Low Frequency layer.
* Use the Clone Stamp Tool (S): Set the Clone Stamp tool to a very soft brush (0% hardness) and a small size. Sample an area near the blemish or discoloration you want to correct (Alt/Option + click). Then, paint over the area to blend it in. Focus on evening out skin tones and removing larger color imperfections.
* Use the Healing Brush Tool (J): Similar to the Clone Stamp, sample an area and paint over blemishes. The Healing Brush attempts to blend the sampled texture with the surrounding area more seamlessly. Again, use a soft brush.
* Use the Mixer Brush Tool: This tool is excellent for smooth transitions and blending colors. Play with settings like Wet, Load, Mix, and Flow to get the desired results.
* Avoid sharpening or blurring the LF layer excessively. Subtle corrections are key.
* High Frequency (Texture/Details):
* Select the High Frequency layer.
* Use the Clone Stamp Tool (S): Set the Clone Stamp tool to a very soft brush (0% hardness) and a very small size. Use this to minimize fine lines, pore visibility (don't eliminate them entirely!), and very fine skin imperfections. Sample nearby skin texture and carefully clone it over the area you want to improve.
* Use the Healing Brush Tool (J): Just like with the LF layer, this can be useful for textures.
* Important: Avoid completely removing texture. The goal is to soften and even out the texture, not create plastic-looking skin. Subtlety is crucial.
Tips for Success:
* Non-Destructive Editing: Consider using a Clone Stamp tool within a new empty layer above your High Frequency and Low Frequency Layers to work non-destructively. Right-click on that new layer and select Create Clipping Mask. Change the empty layer's Blend Mode to Linear Light. Use the All Layers option in the Clone Stamp's Options bar.
* Lower Opacity: Reduce the opacity of the High Frequency or Low Frequency layer if your corrections are too strong. This will blend the edits more naturally.
* Zoom Levels: Work at different zoom levels to see the impact of your edits on the overall image.
* Less is More: The best retouching is often the least noticeable. Avoid over-smoothing or removing too much texture.
* Practice: Frequency separation takes practice to master. Experiment with different blur radii, brush settings, and techniques to find what works best for you.
* Content-Aware Fill: For larger blemishes or distractions, consider using the Content-Aware Fill feature first (Edit > Fill > Content-Aware) before using frequency separation for fine-tuning.
* Don't Forget Lighting: Lighting is essential. If you don't pay attention to highlights and shadows you will end up with unnatural looking skin.
Alternative Method (Using the Median Filter):
Some retouchers prefer using the Median filter for the High Frequency layer instead of the Gaussian Blur/Apply Image method.
1. Follow steps 1-2 above.
2. Select the High Frequency layer.
3. Go to Filter > Noise > Median.
4. Adjust the Radius until the color blotches smooth out. This method tends to preserve skin texture better than Gaussian Blur.
5. Change the Blending Mode of the High Frequency layer to Linear Light.
6. Proceed with the retouching as described above.
Which Method to Use?
* The Gaussian Blur/Apply Image method is more traditional and provides greater control.
* The Median Filter method can be faster and sometimes preserves texture better, especially for fine details. Try both and see which you prefer.
Frequency separation is a versatile technique, but it's just one tool in a retoucher's arsenal. Combine it with other techniques like dodging and burning, color grading, and sharpening for a polished final result. Good luck!