Here's a breakdown of how to perform Frequency Separation in Photoshop:
1. Duplicate Layers:
* Open your portrait image in Photoshop.
* Duplicate the Background Layer twice. You can do this by right-clicking the Background layer in the Layers panel and selecting "Duplicate Layer" or by pressing Ctrl/Cmd + J twice.
* Rename the layers:
* Top Layer: "High Frequency" (or "Texture")
* Middle Layer: "Low Frequency" (or "Color/Tone")
* Bottom Layer: Keep as "Background" (or Original - for comparison)
2. Apply Blur to the Low Frequency Layer:
* Hide the High Frequency layer (click the eye icon next to it in the Layers panel).
* Select the Low Frequency layer.
* Go to Filter > Blur > Gaussian Blur.
* Adjust the Radius until the skin imperfections (blemishes, wrinkles, etc.) are blurred, but the overall shape and color of the face are still visible. You want to blur the details *without* losing the form. The ideal radius will vary depending on the image resolution and the level of detail you want to separate. A good starting point is around 4-8 pixels, but experiment.
* Click OK.
3. Apply Image Calculation to the High Frequency Layer:
* Unhide the High Frequency layer (click the eye icon next to it).
* Select the High Frequency layer.
* Go to Image > Apply Image.
* In the Apply Image dialog box:
* Source: Select the name of your current document.
* Layer: Select the Low Frequency layer.
* Blending: Choose Subtract.
* Scale: Set to 2.
* Offset: Set to 128.
* Invert: Make sure this box is unchecked (unless you're working with a 32-bit image, in which case, check it).
* Channel: Usually RGB or the single channel that looks best for texture.
* Click OK.
4. Change Blending Mode of the High Frequency Layer:
* With the High Frequency layer selected, change its Blending Mode in the Layers panel from "Normal" to "Linear Light". This will reveal the texture details that were extracted. If Linear Light creates harsh results, try "Vivid Light" or "Overlay", but Linear Light is generally the most common and effective.
5. Retouching the Low Frequency Layer (Tone and Color):
* Select the Low Frequency layer.
* Use tools to smooth out color and tonal transitions. Avoid touching fine textures.
* Mixer Brush Tool (Recommended): This is excellent for blending colors and tones while preserving texture. Settings:
* Clean the brush after each stroke (or very frequently).
* Sample All Layers: Unchecked (important - you only want to sample from this layer).
* Wet: Around 10-30% (adjust based on your image)
* Load: Around 5-15% (adjust based on your image)
* Mix: Around 75-90%
* Flow: Around 50-75%
* Click "Sample All Layers" to UNCHECK the box (very important)
* Clone Stamp Tool: Use a soft brush and low opacity (5-15%) to carefully sample and paint over imperfections. Again, sample from the Low Frequency layer.
* Healing Brush Tool: Similar to Clone Stamp, but blends the sampled area with the surrounding pixels. Use with caution, as it can sometimes introduce unwanted artifacts.
6. Retouching the High Frequency Layer (Texture):
* Select the High Frequency layer.
* Use tools specifically for removing texture imperfections without affecting the underlying tones.
* Clone Stamp Tool: This is the most common tool for this layer. Use a small, soft brush and low opacity (5-10%). Sample from a nearby area with similar texture to paint over the imperfection. Sample frequently!
* Healing Brush Tool: Use *very sparingly* on the High Frequency layer. It can blur texture if used aggressively.
* Lasso Tool (for Blemishes): Draw a loose selection around a blemish or imperfection on the High Frequency layer. Then, go to Filter > Noise > Median. Use a very low Radius value (usually 1-2 pixels) to smooth the selected area. Do not use this on large areas, only small blemishes.
7. Important Tips and Considerations:
* Non-Destructive Editing: For a fully non-destructive workflow, you can create a Group (Layer > New > Group) and put both the High Frequency and Low Frequency layers inside. Then, add a Layer Mask to the group to control the overall effect.
* Zoom In!: Work at 100% or even 200% zoom to see the details you're working on.
* Go Slow: Frequency Separation is about subtle adjustments. Don't overdo it!
* Practice: It takes practice to master Frequency Separation. Experiment with different settings and tools to find what works best for you.
* Opacity Control: Adjust the opacity of the High Frequency and/or Low Frequency layers to fine-tune the overall effect.
* Masking: Use layer masks to selectively apply the retouching to specific areas of the image. This is especially important for preserving texture in areas like hair, eyebrows, and eyelashes.
* Compare to the Original: Periodically hide the Low Frequency and High Frequency layers to compare your progress to the original image and make sure you're not losing too much detail or creating unnatural effects.
* Image Resolution: Frequency Separation works best on high-resolution images. If your image is low resolution, the blur in the Low Frequency layer might remove too much detail.
* Global Adjustments: After retouching using Frequency Separation, you can still apply global adjustments (e.g., Levels, Curves, Color Balance) to the entire image to refine the overall look and feel.
Example Workflow:
1. Duplicate Background Layer twice.
2. Rename to "High Frequency" and "Low Frequency".
3. Hide "High Frequency".
4. Select "Low Frequency".
5. Filter > Blur > Gaussian Blur (Radius: 4-8 pixels - adjust as needed).
6. Unhide "High Frequency".
7. Select "High Frequency".
8. Image > Apply Image (Source: Current Document, Layer: Low Frequency, Blending: Subtract, Scale: 2, Offset: 128).
9. Change High Frequency Blending Mode to "Linear Light".
10. Retouch Low Frequency layer with Mixer Brush to even out skin tones.
11. Retouch High Frequency layer with Clone Stamp to remove blemishes, using a very small, soft brush and sampling frequently.
12. Periodically compare to the original.
13. Adjust layer opacities and add masks as needed.
14. Apply global adjustments.
By following these steps and practicing regularly, you can effectively use Frequency Separation to achieve natural and professional-looking portrait retouching results. Remember to aim for subtle improvements and to preserve the natural texture and character of the subject.