Frequency Separation
A retouching technique that splits an image into a blurred low-frequency layer of tone and colour and a high-frequency layer of texture.
Measured in
px (radius)
In depth
Separating the two lets a retoucher smooth uneven shading without touching pore detail, or clean up texture without altering skin tone. It is powerful and easily abused: over-flattening the low-frequency layer produces the airbrushed, mannequin-like skin that marks amateur beauty retouching.
Examples in practice
Evening out blotchy colour on the low-frequency layer leaves every pore intact on the layer above.