Split Frequency Healing is a technique used in Photoshop to
retouch photos without affecting the photo's respective tone or texture.
Healing and cloning both have their advantages
and disadvantages. The Healing tool will copy texture from one
area and then merges the texture into the color and
luminosity of the
destination area.
The advantage is that you can use it on an empty layer and
get natural looking results.
The disadvantage is that you can’t control the
amount of texture or the amount of
merging.
The Clone tool
doesn’t make this distinction and just pastes texture and color into the
destination area.
The advantage is that it can be used on an empty layer
blended “darken” or ”lighten”
and limit the effect, getting good looking
results.
The disadvantage is that you can’t “clone” only texture.
Split Frequency splits an image into its
visual frequencies using two layers, one to capture texture (High Frequency) and
the other for toning and color (Low Frequency). In this way texture can be
manipulated without affecting tone and contour and tones and luminosity
can be corrected without altering texture.
To split an RGB image into it's low and high frequencies create
two copies of the image (Cmd/Ctrl J twice) or (Cmd/Ctrl+Option/Alt +Shift+E to
merge layers and then Cmd/Ctrl J twice). Name the top one High and the lower
one Low.
Working on the Low layer apply a Gaussian Blur filter to blur to
suit but around a setting of 15 is a starter. The RIGHT
radius is the one that smooths sufficiently for the look required.
On the High layer go to Image-Apply Image and
apply the following settings:-
Settings for 16 bits:
Settings for 8 bits:
Make sure in the box marked Layer it is the layer below named Low. Click OK.
The HIGH layer will now look like a High
Pass. Set the Blend Mode of the layer to Linear Light. Opacity and Fill should
remain at 100%.
Taking the layers together it will look exactly
as your
original image.
The only difference is that your image data is now
separated into two frequencies:
HIGH containing detail and LOW containing
shape.
The layers may be grouped to keep them together.
We can now use the Healing and Clone tools
but make sure the Clone Sample mode is set to Current Layer.
What can be done on the HIGH layer?
Use the Healing brush (hard edge to avoid blurred texture). Always use a bigger brush
than the texture to be replaced. Blend texture with texture. Use the Clone brush
(usually with soft edges) in normal and both darken and lighten mode, but now,
only for texture.
Use the Patch Tool to replace texture.
Clipping different
curves for different effects.
What can be done on the LOW layer?
Using the Healing and Cloning tools in the usual way to replace, smooth or contour color
and shading. Create a new layer over it and paint in normal mode, on low
opacity to even
out tones.
Create a duplicate of the LOW layer.
Blur it
further to eliminate middle frequencies.
Mask and paint with white on the mask
to reveal the effect where needed.
This is called “Band Pass” and it has a lot
of variations.
The most important part of this technique is
that texture is maintained or created whilst toning is created without the two
affecting each other. Some experimentation will be necessary to become
proficient.
