Image Sharpener
Bring back crispness to photos that look a little soft, especially after resizing or scanning. Start from a preset, fine-tune the strength, and compare with the original before you download.
- Files stay on your device
- No sign-up
- Free to use
Judge sharpness at 100% zoom: the preview is scaled to fit your screen, which hides fine detail.
Sharpening
Amount sets the strength, Radius the size of the edges affected, and Threshold protects smooth areas such as skin and sky from added noise.
Output
How to use Image Sharpener
- Drop one or more images onto the upload area.
- Pick a preset: Subtle for portraits, Standard for most photos, Strong for soft scans, or After resizing for downscaled web images.
- Fine-tune Amount, Radius and Threshold while watching the preview, and hold the compare button to see the original.
- Select Sharpen images and download the results.
Image Sharpener features
Unsharp mask
The same technique professional editors use: edges are found by comparing the photo with a blurred copy, then their contrast is increased.
Three precise controls
Amount sets the strength, Radius the width of the edge halo, and Threshold protects smooth areas from grain.
Presets for common jobs
Starting points for portraits, everyday photos, soft scans and images that were just resized.
Noise-aware
The threshold leaves skin, sky and other gentle gradients untouched, so sharpening does not add grit.
Consistent everywhere
The filter is calculated pixel by pixel, so results are identical in every browser.
Private
Images are processed on your device and never uploaded.
When to use Image Sharpener
- Restoring crispness to photos that were reduced in size for a website or online shop.
- Improving slightly soft shots taken with a phone in low light.
- Making scanned prints and documents look cleaner.
- Preparing product photos so textures and edges stand out.
- Adding final output sharpening before printing.
Image Sharpener FAQ
Can this fix a really blurry photo?
No sharpening tool can recover detail that was never captured. Sharpening increases contrast along existing edges, which makes slightly soft images look crisper. Strong motion blur or a badly missed focus will look harsher, not clearer.
What do Amount, Radius and Threshold do?
Amount controls how much contrast is added at edges. Radius controls how wide the affected area around each edge is: small values sharpen fine texture, large values add punch to bigger shapes. Threshold sets how different neighbouring pixels must be before they are treated as an edge, which keeps smooth areas clean.
How do I know if I have over-sharpened?
Look for bright or dark halos along edges, a crunchy look in hair and foliage, and visible grain in skies. Reduce Amount first, then Radius. Checking the image at its real size is the most reliable test.
Should I sharpen before or after resizing?
After. Resizing softens the image, so sharpening is best applied as the final step at the size the image will be viewed or printed. The After resizing preset is tuned for that.
Does sharpening increase file size?
Slightly, for JPG and WebP. Sharper detail is harder to compress, so expect files to grow by a few per cent.
How unsharp masking makes photos look sharper
The name sounds backwards, but it comes from the darkroom. Photographers made a slightly blurred, or unsharp, negative copy of a photo and sandwiched it with the original during printing. Where the image was flat, the two cancelled out; along edges, where the blurred copy differed from the original, contrast increased. Digital unsharp masking does the same arithmetic: subtract a blurred version from the photo to isolate edges, then add a multiple of that difference back.
Our eyes judge sharpness mostly by edge contrast, a property called acutance, rather than by resolution. That is why a modest amount of sharpening makes a picture look clearer even though no new detail is created. It is also why over-sharpening is easy to spot: the light and dark bands placed along each edge become visible halos, especially around high-contrast outlines such as a dark building against a bright sky.
The three settings interact. A small radius, below one pixel, targets fine texture such as hair, fabric and foliage. A larger radius affects broader shapes and can give flat images more depth, a technique sometimes called local contrast enhancement when the radius is very large and the amount low. The threshold works as a gate: differences smaller than its value are treated as noise or smooth gradation and left alone.
Sharpening belongs at the end of an editing workflow. Crop, adjust brightness and colour, resize to the final dimensions, and only then sharpen for the medium: a little for screens, more for matte paper, which absorbs ink and softens detail.