How the high pass skin smoothing effect works
Ok so now you have a good understanding of how the high pass filter works because you read the introduction and how to sharpen your photos with a high pass right? 😉 Don’t worry, if you haven’t you’ll still get a lot out of this tutorial. Essentially this is a method for smoothing out skin details and removing blemishes in portrait photos.
A very common method for smoothing skin tones is to use the Gaussian blur filter and to change blending modes. The problem with that method is it increases color saturation and contrast. While this can be a good look for those ‘high key’ portraits I like to keep these methods of control separate. I like to control contrast and color saturation using other methods rather than have them dictated to me by the skin smoothing technique. This is where using the inverted high pass technique excels.
When the high pass filter is used to sharpen an image it increases edge contrast but leaves the surface areas alone. The technique described in this tutorial does the exact opposite of that. By inverting the high pass layer and changing a few of the settings the effect reverses. Instead of sharpening edge details and leaving the surface areas untouched, the effect is to smooth the surface areas and leave the edge details alone. This is great for portraits where the aim is often to create a flattering perspective of the subject with good detail in the eyes and hair but smooth transitions in the skin tones.
This is all thanks to the Overlay blending mode. When you invert a layer that is using this blending mode it subtly brightens the darker tones and subtly darkens the lighter tones. If we apply this to the example of a portrait, the effect will be to slightly brighten the darker shades (the subject’s skin pours) whilst slightly darkening the brighter parts of the skin tones (the skin that is closer to the light source). This all happens at the close-up level, but when viewed from a whole, the effect is a softer appearance of surface areas.
Photoshop Video tuts
This video quickly demonstrates how to use the inverted high pass technique. It is intended to accompany the ‘how-to’ steps below.
If you found this instructional video helpful please check out photoshop mac download and the photoshop nerd YouTube channel.
How to smooth skin tones using the inverted high pass filter
Step 1) Duplicate the layer.
Step 2) Go to filter>other>high pass. Choose a radius of between 6-10 pixels (Note that this is roughly double the radius normally used for sharpening).
Step 3) Desaturate the layer: image>adjustments>hue/saturation or (ctrl + shift + U).
Step 5) Invert the layer: image>adjustments>invert or (ctrl + [the letter I]).
Step 6) Lower the opacity – start around 50% and increase if you want a smoother effect.
Step 7) Add a mask to the layer.
Step 8) Choose the brush tool (B). With the layer mask selected, paint with black over the areas of the image that you don’t want to be softened by the effect (for example the eyes and hair).
The image in masking mode
That’s it! That was so easy, right? The best part of this is that it doesn’t affect color or contrast, instead, the inverted high pass technique smooth’s out the micro transitions. That’s why it’s so effective for portraits because often those wrinkles and blemishes are only very small details and by inverting the high pass you are effectively reducing the local contrast in that area. Better still you don’t have to be very careful with your layer mask. As you can see in step 8 (depicting a mask when in masking mode), I have done a poor job of masking the details. It doesn’t matter since the nature of the high pass filter means it has already done a good job of not affecting the detailed areas. It just requires a few finishing touches to completely remove it from edge details.
Download free photoshop actions
As usual, I have built all of these steps into action for skin smoothing. And as usual, I recommend checking out the instructional video above and learning the steps involved. Actions are great for speeding up workflow however it’s always best to have a solid understanding of how things work inside of Photoshop.
This completes part 2 of the high pass series. In part 3 I’ll demonstrate how to use the high pass filter to mimic the grungy tone-mapped look of HDR images.