Reducing and adding noise in Paint by Zaweba

Noise is the speckle you see in photos taken in low light, the blocky smudges around edges in a heavily compressed JPEG, and the dust spots on an old scan. It is also, sometimes, exactly what you want: film grain gives a picture texture and hides banding in smooth gradients. The Noise filters in Paint by Zaweba handle both directions, taking noise out and putting it in.

Taking noise out

Reduce Noise is the main clean-up filter. It smooths random speckle while trying to hold on to real detail. It can work on each channel separately, which matters because digital noise is often much worse in one colour channel than the others, typically the blue. Cleaning that channel harder while leaving the rest gentle keeps more detail than treating everything the same. It also has an option for JPEG artefacts, the blocky patterns and ringing that heavy compression leaves around edges and in skies.

Despeckle is a quick, settings-light version that softens small specks while keeping edges. It suits scanned prints with a fine paper texture.

Dust and Scratches looks for small spots and thin lines that differ sharply from their surroundings and fills them in. It is the go-to filter for old scanned photographs and slides. Use it on a selection or a masked duplicate layer, because over a whole picture it can soften fine detail along with the dust.

Median replaces each pixel with the middle value of its neighbours. It is very good at removing isolated specks and also makes a quick way to smooth a mask or simplify a texture.

Putting noise in

Add Noise sprinkles fresh noise across the picture. A small amount stops smooth gradients from banding when you export to 8-bit formats, and helps a retouched area match the grain of the rest of the photo.

Photo Grain imitates the grain of film rather than plain digital noise, for a softer, more organic texture. New Grain Layer puts grain on a layer of its own, so you can change its strength with opacity or remove it later without touching the photo. That is the more flexible approach when you are not sure how much grain you want.

HSV noise and LCh noise vary the colour of pixels by hue, saturation and lightness rather than adding plain speckle, which can give a gentle, painterly shimmer. Hurl, Pick, Slur and Spread are older-style effects that scatter, swap or smear pixels. They are more creative than corrective and are useful for rough textures, distressed type and glitchy backgrounds.

A good order of work

Reduce noise early, before sharpening and before big tonal changes. Sharpening exaggerates noise, so cleaning first gives a better base.

Judge at 100 per cent zoom. Noise reduction always looks fine at fit-to-screen. Up close you can see whether skin has turned to plastic or fine textures such as hair have vanished.

Bring back a touch of grain at the end. A photo with every trace of noise removed often looks artificial. A light Photo Grain or a grain layer at low opacity restores a natural feel.

Mistakes to avoid with noise

Heavy noise reduction over a whole picture is the most common mistake. Use a selection or a mask so smooth areas like skies get strong treatment and detailed areas get less. With Dust and Scratches, too strong a setting removes eye catchlights and fine hair, so check those first. And when adding grain for a print, test at print size; grain that looks right on screen can vanish or look harsh on paper.

The Noise filters work with Edit > Fade, so you can lower a filter's effect straight after applying it, and with the rest of the retouching tools in Paint by Zaweba for the spots a filter cannot fix.