How to sharpen a photo without halos

Sharpen a photo in six steps

1. 1

   Open the photo and zoom to 100%

   Open the photo with File› then Open… (Ctrl+O or ⌘O); to follow along, open the sample from this page. Then press Ctrl+1 or ⌘1 (View› then Actual Size (100%)) so one image pixel is one screen pixel, and pan to an area with fine detail and a strong edge. On the sample: the eyes and the ear against the bright window.

   If you will make the photo smaller for the web, resize it first and sharpen after: sharpening is tuned to the final pixel size.

2. 2

   Convert the layer to a Smart Object

   Choose Layer› then Smart Objects› then Convert to Smart Object. Filters applied to a Smart Object are kept as editable Smart Filters, so you can lower the amount later, for example after seeing a print. Skip this step if you are sure.

   

3. 3

   Choose Filter › Sharpen › Smart Sharpen…

   The Sharpen submenu holds every sharpening tool. Smart Sharpen is the best start for photos: it reverses blur instead of only boosting edge contrast, and it protects grain. The other tools are compared below.

   

4. 4

   Set Amount, Radius and Remove

   • Amount (default 150%): how strong the sharpening is. Watch the eyes and fur while you change it.
   • Radius (default 1 px): how wide the blur is that it reverses. For most photos 0.5–2 px is right. Larger values sharpen broader shapes but draw halos quickly.
   • Remove: the kind of blur. Lens Blur (the default) suits normal softness from focus or a lens. Motion Blur reverses a short shake in one direction, set by Motion angle. Gaussian Blur is simple edge contrast, like Unsharp Mask.
   • Reduce noise (default 10%): holds back sharpening in low-contrast areas, where grain lives. Raise it for high-ISO photos.

   On the sample the defaults already work: the fur and the eyes gain detail. Turn Preview off and on to compare.

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5. 5

   Check the edges for halos

   Now look at a high-contrast edge, such as the ear against the bright window. A light line along the bright side, or a dark line along the dark side, is a halo: the sharpening has overshot.

   If you see one, lower Amount first, then Radius. The right-hand picture below is what too much looks like: Smart Sharpen at an Amount of 400% and a 3 px Radius.

   

6. 6

   Apply and export

   Click Apply. Then export with File› then Export› then JPEG… or save the editable version with File› then Save As› then Lil Cactus Project… (Ctrl+Shift+S or ⇧⌘S). Sharpen once, as the last step: sharpening a photo that was already sharpened, by the camera or by you, multiplies halos and grain and gives a crunchy, painted look. Many cameras and phones already sharpen their JPEGs, so go easy on those.

Keep halos out of bright and dark areas

Below the main controls, Smart Sharpen has Shadows and Highlights groups. Highlight fade reduces sharpening in the brightest tones, and Shadow fade in the darkest tones, where sharpening mostly raises noise. The tonal width controls decide how far up or down the range counts as a highlight or shadow (default 50%), and the radius controls how large an area is judged. Both fades start at 0%, meaning off. Their effect is gentle: on the sample at 50%, Shadow fade trims dark outlines by about a fifth and Highlight fade trims bright ones by about a tenth.

Unsharp Mask: the classic method

Filter› then Sharpen› then Unsharp Mask… blurs a copy of the photo, takes the difference from the original, and adds that difference back, multiplied by Amount. It is predictable and quick.

• Amount (default 80%): strength. 80–150% for photos.
• Radius (default 2 px): how far from each edge the effect reaches. 0.5–1.5 px for fine detail.
• Threshold (default 0): differences smaller than this are left alone, so smooth skin and skies stay smooth while edges sharpen. 2–6 is a good range for portraits and grainy photos.

Unlike Smart Sharpen it has no blur model and no noise protection beyond Threshold.

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High Pass, Multi Band Sharpen and the one-click filters

• High Pass on a layer: duplicate the layer (Layer› then Duplicate Layer, Ctrl+J or ⌘J), run Filter› then Sharpen› then High Pass… on the copy with a Radius of 1–3 px (it turns gray, with edges drawn in light and dark), then set the copy’s blend mode to Overlay or the gentler Soft Light in the Layers panel. Opacity controls the strength, and painting black on a mask removes the sharpening where you don’t want it.
• Multi Band Sharpen (Filter› then Sharpen› then Multi Band Sharpen…): enhances detail at five scales at once with Multiscale (five scales), the default, which also strengthens broader texture such as bark or rock; Fine scale only limits it to the finest detail. It may amplify grain; use Amount (default 35%) to control it.
• Sharpen and Sharpen Edges: one-click filters with no settings.

How much sharpening for screen and print

• Web and social media: sharpen lightly (Smart Sharpen around 80–150%, Radius 0.5–1 px), judging at 100%.
• Print: printing softens detail, so a photo that looks just right on screen usually prints slightly soft. Sharpen a little more than looks ideal at 100%, but still without visible halos.
• Portraits: sharpen eyes, lashes and hair, and keep skin smooth: Threshold in Unsharp Mask, or a High Pass layer with black painted on its mask over the skin.

What to do next

• Clean up grain before sharpening: how to reduce noise.
• Resizing for the web? Resize the image.
• Shooting RAW? Develop it first: how to edit a RAW photo.
• Use a layer mask to sharpen only part of the photo.

Coming from another editor

Photoshop

Filter › Sharpen › Smart Sharpen… and Unsharp Mask…, the same menu paths as in Lil Cactus.

GIMP

Filters › Enhance › Sharpen (Unsharp Mask)… In Lil Cactus it is Filter › Sharpen › Unsharp Mask…, or Smart Sharpen… beside it.

Photo sharpening: questions and answers