How to Sharpen an Image in GIMP
Not every soft photo is a lost cause. GIMP has two sharpening tools that can recover detail and make an image look crisper - And knowing which one to reach for makes a big difference in the result. This guide covers both, the settings that work for most photos, and how to spot when you have gone too far.
The Two Sharpening Tools in GIMP
| Tool | Where to Find It | Best For |
|---|---|---|
| Unsharp Mask | Filters - Enhance - Unsharp Mask | Most photos - More control over the result |
| Sharpen (legacy) | Filters - Enhance - Sharpen | Quick, single-slider sharpening for simple fixes |
Unsharp Mask is the better tool in almost every case. The name is counterintuitive - It sounds like it blurs things - But it actually sharpens. The name comes from the darkroom technique it is based on.
Using Unsharp Mask
Go to Filters - Enhance - Unsharp Mask. A dialog appears with three sliders:
- Radius - How far out from each edge the sharpening effect spreads. For web images use 0.3-0.8. For print images use 1.0-2.0.
- Amount - The strength of the sharpening. Start at 0.3-0.5 and increase carefully. Going above 0.8 often looks artificial.
- Threshold - How different two adjacent pixels need to be before sharpening is applied. A value of 0 sharpens everything including noise. 3-5 avoids sharpening smooth skin or sky areas.
Starting Settings by Image Type
| Image Type | Radius | Amount | Threshold |
|---|---|---|---|
| Portrait (face) | 0.5 | 0.3 | 5 |
| Landscape / architecture | 0.8 | 0.5 | 2 |
| Product photo (web) | 0.5 | 0.4 | 0 |
| Print (high res) | 1.5 | 0.5 | 3 |
Sharpening Only Part of the Image
For portraits, you usually want to sharpen the eyes and hair but leave the skin smooth. To do that:
-
1Use the Free Select tool to draw a rough selection around the eyes or the detail area you want to sharpen.
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2Feather the selection (Select - Feather, 10-20 px) so the effect fades in gradually rather than cutting off sharply.
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3Apply Unsharp Mask. The effect only touches the selected area.
Sharpening works best as a final step after all other colour and exposure adjustments are done. The photo editing guide shows the full recommended order of operations for getting the most out of a photo in GIMP.
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