Frequency Separation Retouching

The principle of Frequency Separation Retouching relies on the differences between the two
concepts: High frequency images are detailed, and sharp, and low frequency images are
blurred, soft and contain only the tones of the image… no skin detail.

This is the image that I am re-touching

Retouch with layers (1) jpeg

To start with, create two additional layer copies, and call these layers “Low Frequency” and
“High Frequency”, then switch off the background layer and keep it as a back-up layer in case
anything goes wrong.

First of all we’ll create the Low Frequency layer, and this is very simple. We simply blur it. Use
Filter/blur/Gaussian blur. I chose a setting of 20 pixels, but it will vary from image to image
depending on image resolution.

This is your low frequency layer. You need to switch off the high frequency layer to see this
effect as it is above the low frequency layer in the stack. Once created, switch the high
frequency layer back on.
Next we need to create the High Frequency layer.
Select the High Frequency layer, and then use Image/Apply Image.
Depending on whether you are using a 8bit image, or a 16bit image, the settings you need are
different. The image we are using today is 16bit, but when you are using your own images,
please check by using Image/Mode to see what bit depth you are using

We select the low frequency layer and either add or subtract it from the high frequency layer
depending upon bit depth. We also invert the RGB channels if 16bit.
What this gives us is a layer with all the low frequency detail removed, and only the high
frequency detail intact against a 50% grey background… rather like using a High Pass filter to
sharpen, but the edge contrast still has colour information.

We then select the “linear light” layer blend for the High Frequency layer. This returns
everything to normal, by adding the high frequency information to the low frequency
information so the two layers effectively reconstruct the original image.

We are now ready to start airbushing the low frequency layer in order to smooth the skin
tones.As always, we seek ways to use layers to make as many of the stages as non-destructive as
possible, so we will create a new layer above the low frequency layer, and call this “low
frequency retouch”.

There are many ways in which people retouch this low frequency layer, but perhaps the
simplest and easiest way is to merely paint with a brush. First, we need to set up the dropper
tool to sample the colours from the low frequency layer.

Select the dropper tool

Then select the context menu s below.
Then select the new layer you called “Low frequency retouch”.Select the paintbrush tool, and use a reasonably large brush with minimum hardness set.
Remember though, that you can, and should alter the size of the brush as you are airbrushing
to suit the area of the face you are working on. You can quickly alter the brush size with the [
and ] keys.
With the paintbrush selected, press and hold “alt” while you sample a skin colour close to the
area you wish to airbrush.
Then let go and start airbushing. You will notice that the skin detail is not changes at all, but
you are smoothing out the skin tones underneath. Resample very often with the Alt key, and
try to follow the natural tones of the skin as they are in reality. Remember… You’re painting
now, and painting requires skill. You may need to practice at this until you get the technique
right.BeforeAfter
We’ve only modified the low frequency layer. The detail, being contained in the high frequency
layer is untouched.
As we had the dropper tool set to “current & Below” for its sampling, all our airbrushing is in
one layer… the High Frequency Retouch layer’. Continue to airbrush as you see fit. If you
make a mistake, or decide you don’t like it, you can just erase the layer’s contents, or delete the
layer and start again.
Once the low frequency layer is airbrushed to smooth the skin, we can now retouch the high
frequency layer in order to retouch flaws, spots, creases… in fact anything we want.Create a new layer and call it “High Frequency Retouch”
Select whichever retouch tool you prefer… Spot Heal, Heal, or Clone Stamp (or switch between
them as necessary) and makes sure the context menu says “Current and below” for Heal and
Clone, or “Sample all layers” for the spot heal tool
As you are sampling everything below, it is advisable that you are completely finished and
happy with your low frequency retouching before you begin this stage, as going back and
reworking the low frequency airbrushing layer may reveal your high frequency retouching if the
colour changes.
Select the High Frequency Retouch layer and begin retouching. If you are using the Heal or
Clone tools, resample VERY frequency with the Alt key to avoid patterning. Use VERY small
brushes and literally retouch almost at a skin pore level of resolution. There is NO quick fix for
this stage. A typical facial retouch takes around 30 minutes for an experienced Photoshop user,
so expect this to take more your first time. At this level, avoid clicking and dragging the retouch
tools to “draw” with them.. instead, single clicks over the biggest pores, or spots individually.
Again, as we are on a new layer, all our high frequency retouching is contained within that layer
and can be deleted any time.

This is my final re-touched image .
Retouch with layers (1) newcurvesjpeg

Using either dodge, or burn tools, and various sized, soft brushes, lighten or darken as
appropriate.

2 Comments on “Frequency Separation Retouching

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