How to sharpen photos well in Paint by Zaweba
Unsharp Mask, Smart Sharpen, High Pass and Shake Reduction in Paint by Zaweba: which sharpening filter to use, and how to avoid halos.
Almost every photo benefits from a little sharpening, and almost every over-processed photo has had too much. The goal is crisp detail without bright halos, crunchy noise or that brittle digital look. Paint by Zaweba has several sharpening filters, each suited to a different situation, all with the usual live preview and Strength control.
Unsharp Mask
Despite the name, Unsharp Mask is the classic sharpening tool. It finds edges and increases the contrast across them. The craft lies in balancing how strong that contrast is, how far it spreads either side of an edge, and keeping it away from very small differences such as noise or smooth skin.
For general photo sharpening, keep the spread small so you sharpen fine detail rather than whole outlines. A wider spread at a lower strength gives a different, punchier result sometimes called local contrast, which can add depth to landscapes.
Smart Sharpen
Smart Sharpen offers more control over what kind of blur you are correcting. You can choose a Gaussian model for general softness, a lens model for the slight blur most lenses produce, or a motion model when the blur has a direction. It also has shadow and highlight fade, which reduce sharpening in the darkest and brightest areas. That is where halos and noise tend to show first, so fading there lets you sharpen the mid-tones more without ugly side effects.
High Pass
High Pass is less a sharpening filter than a building block. It turns the picture grey except for the edges. Put it on a duplicate layer, set that layer's blend mode to one of the contrast modes such as Overlay or Soft Light, and the edges in the picture below become crisper. Because it sits on its own layer, you can mask it to sharpen only the eyes in a portrait, or lower the layer opacity to adjust the strength at any time.
Shake Reduction
Shake Reduction tackles a specific problem: a photo blurred because the camera moved in a straight line during the exposure. It estimates that straight shake and reverses it by deconvolution. On the right picture it can bring back readable text or a recognisable face. It cannot fix every blur, for example when the subject moved rather than the camera, or when the shake was a curve, so judge the preview honestly.
At the simple end, Sharpen, Sharpen More and Sharpen Edges are one-click filters with fixed strengths. They are quick for small web images where you just want a touch more bite, and Sharpen Edges leaves smooth areas alone.
Sharpening without the halos
Sharpen last. Do your colour, tone and retouching first, resize the image to its final size, and then sharpen for that size. Sharpening before resizing wastes the effort, because resizing softens or exaggerates it.
Look at 100 per cent zoom. Sharpening judged at fit-to-screen is almost always too strong.
Protect skin and skies. Use a mask on a High Pass layer or a selection, so smooth areas stay smooth and only textured areas such as hair, eyes, fabric and foliage get sharpened.
If you see bright outlines along dark edges, the sharpening is too strong or too wide. Back it off, or use Smart Sharpen's highlight fade.
Where sharpening fits
Sharpening is the finishing step in most photo workflows in Paint by Zaweba, after the adjustments and the retouching. Noise reduction usually comes before it, since sharpening noise only makes it worse. Use Edit > Fade straight after if the result needs to come down a notch.
