Retouching by scale with Wavelet Decompose in Paint by Zaweba

Frequency separation splits a picture in two: fine texture and broad colour. That is enough for many jobs, but real blemishes come in all sizes. Pores are tiny, spots are small, blotches are medium-sized and uneven shading is large. Wavelet Decompose goes further and splits a layer into a whole ladder of detail scales, so you can work on one size of problem without touching the others.

You run it from Filter > Wavelet Decompose in Paint by Zaweba.

What it makes

The command turns the layer into a group of layers. Each detail layer holds the features of one size, from the finest to the coarsest, and they sit in Linear Light blend mode over a residual layer that holds whatever is left: the broad colour and light of the picture.

The important property is that they add back to the picture exactly. Before you change anything, the group looks identical to the layer you started with. Only when you edit one of the scales does the picture change, and only at that size.

The whole operation is one undo step, so if you decide against it, a single undo returns you to the original layer.

Why scales help

Suppose a face has a few red blotches, about the size of a fingertip at the picture's resolution. On an ordinary layer, smoothing them also blurs the pores in the same place. With the picture decomposed, the blotches live mainly on one or two middle scales, while the pores live on the finest. Soften the middle scale over the blotch and the pores stay exactly as they were.

The same goes for other jobs. Uneven lighting across a backdrop sits on the coarse scales and the residual; you can smooth it there without touching the backdrop's texture. Fine wrinkles in a shirt sit on small and middle scales; you can soften them there while keeping the weave.

A way to work

Hide all the scales except one to see what it contains. That quickly shows which scale holds the problem you want to fix.

On that scale, use a gentle blur on a selection, a soft clone or healing brush that samples only the current layer, or a soft brush in neutral grey at low opacity, which reduces the detail at that scale towards nothing. Work with care at low strength and build up. Then turn all the layers back on and check the whole picture.

Keep the finest scales mostly untouched on faces. That is where skin texture lives, and removing it gives the plastic look that makes retouching obvious.

Use the residual layer for colour and tone: evening out redness or lighting with a soft brush. Since the residual has no fine detail, painting on it doesn't affect texture at all.

Comparing with frequency separation

Paint by Zaweba has Frequency Separation as well, under the Layer menu. It is simpler: two layers, quick to set up and enough for most skin retouching. Choose Wavelet Decompose when a picture has problems at several sizes, when you want to fix something without touching a texture that is close to it in size, or for detailed product and beauty work where precision matters.

Many retouchers use both: frequency separation for a quick pass, and wavelets for a portrait that will be printed large.

Beyond portraits

Wavelet scales help wherever detail and tone need separate treatment. Clean dust from a textured surface on the right scale. Reduce moiré patterns that sit at one size. Add texture back to an area by duplicating a fine scale. Sharpen only medium detail by raising the contrast on one scale.

Because the result is a normal group of layers, it is saved with your document and you can return to it any time. Wavelet Decompose is a precise tool, and once you are used to thinking in scales it becomes one of the most useful in the retouching kit.