What do radius, amount and threshold actually do?

An unsharp mask blurs a copy, subtracts it from the original and adds a scaled difference back to each RGB channel. Radius is the Gaussian standard deviation, from 0.1 to 10 pixels. Amount is 0 to 300 percent; 100 adds the difference once and 0 leaves the decoded canvas pixels unchanged. Threshold is 0 to 255 and skips a channel when its absolute difference is smaller. Defaults are radius 1.2, amount 85 and threshold 4; they are an editable example, not settings for every photo.

How do I sharpen a photo without halos?

Compare the result at the size you will use it, reduce Amount if edge rims become visible, and try a smaller Radius if the rims are broad. Threshold skips small channel differences and can reduce changes in flatter areas, but it does not guarantee that noise or halos disappear. The tool warns above amount 150. The worked examples show the same edge at amount 85 and 300 so you can compare the effect.

Can a blurry photo be fixed?

The unsharp mask can make existing edges more distinct, but it cannot recover detail lost through missed focus, movement, compression or enlargement. Stronger settings can amplify noise and artefacts. This tool does not deblur, upscale, remove noise or generate replacement detail. Use the comparison divider to judge the actual changes rather than treating a stronger edge as recovered information.

Is transparency preserved?

The unsharp operation retains the alpha values from the decoded canvas image, and its blur weights neighbouring pixels by alpha. PNG export retains that transparency. Browser decoding, colour conversion and canvas handling can affect the source data before sharpening, so this does not promise byte-identical source pixels. JPEG has no alpha; the page warns that transparency will be filled with white before saving it.

Is my photo uploaded?

No. The file is read by the page itself, decoded by your browser, drawn onto a canvas and sharpened in memory. There is no server in this and no endpoint for an image to go to, nothing about the picture is sent to analytics, and nothing about it is written into your browser's storage: the tool remembers your radius, amount and threshold between visits, and that is all it remembers.

How large an image can it sharpen, and what comes out?

Up to 30 megapixels, which covers a 6,000 by 5,000 frame. A larger file is refused in words, with the megapixel size it read and the ceiling, rather than being quietly shrunk to fit; resize it first and sharpen the smaller copy. What comes out has exactly the same pixel dimensions as what went in, because sharpening changes values and not geometry. The download is your own file name with -sharpened on the end, as a PNG, or as a JPEG written at 0.92 quality when you choose that instead.

How do I sharpen an image in Photoshop?

In current Photoshop desktop, select the image layer, convert it to a Smart Object if you want to edit the filter later, and inspect the image at 100% zoom. Choose Filter > Sharpen > Smart Sharpen. Adjust Amount and Radius, set Reduce Noise if needed, choose the appropriate Remove blur option, preview the effect and select OK. This is a Photoshop instruction, not an edit to a Photoshop document by this page; no method promises to reconstruct missing detail.

How do I sharpen an image in GIMP?

In GIMP 3, open the image and choose Filters > Enhance > Sharpen (Unsharp Mask). Adjust Radius, Amount and Threshold while previewing the result, then apply the filter. GIMP uses its own ranges and image pipeline, so do not copy this page's slider numbers as equivalent GIMP settings. This page processes a local raster image separately.

Can I sharpen PNG, JPEG, screenshots or text in a raster image?

Use a file your browser can decode, commonly PNG or JPEG, or paste a screenshot when the browser permits it. The same mask acts on existing pixel edges, including raster text; it does not recognize or replace letters. PNG can retain transparency, while JPEG uses a white background and lossy encoding. SVG/vector editing and PDF-document sharpening are separate workflows.

Is this AI sharpening or image upscaling?

It uses the stated Gaussian unsharp mask, with no inference model, generated detail or change of image dimensions. It cannot perform AI reconstruction, enlarge a picture, sharpen just a selected region, or repeat a blur/sharpen operation automatically. Radius, Amount and Threshold apply to the whole decoded image.

Can I use it on iPhone, Windows or without a watermark?

Open this page in a current browser and choose a decodable image from the device file picker. Clipboard image support varies, so use the picker if paste is unavailable. The output contains no added watermark, and the core requires no sign-up. This is a browser tool, with no installed sharpening application or access to your device photo editor.

Will sharpening leave every colour unchanged?

No. This mask changes RGB channel values to increase local edge contrast. Its alpha handling preserves decoded transparency, but it has no luminosity-only mode or colour-profile preservation guarantee. The screen comparison shows the actual decoded and processed images; it does not certify unchanged colours or print appearance.

Image Sharpen

Choose, drop or paste a raster image, then adjust the unsharp mask and drag the divider to compare before and after. Radius controls the Gaussian blur in pixels, Amount scales the added detail and Threshold limits which differences are changed. Processing and output use the decoded image dimensions, up to 30 megapixels.

no image yet

or drop one here, or paste a screenshot

Never uploadedTransparency keptNo accountUp to 30 megapixels

Radius: 1.2 px
Amount: 85 %
Threshold: 4
Save as

One edge, amount 8560 against 200, radius 1, threshold 4
becomes 24 against 236, a step of 212 instead of 140
The same edge, amount 300the overshoot runs off both ends
0 against 255: a flat rim, which is what a halo is
A cut-out on transparencyflat colour, alpha 0 around it
every pixel identical, no rim along the alpha edge

Those three lines are printed by running the same code your picture goes through, not typed in by hand.

Your image stays on this device. An unsharp mask raises contrast along edges that are already in the image. It cannot recover detail the camera never recorded, so a blurred or heavily compressed photo cannot be made sharp, and a high amount produces bright halos along hard edges rather than more detail. Images up to 30 megapixels are accepted. There is no upload, no account and no watermark, and no image byte is handed to analytics either: the only thing the page records is that the tool was used.

Common questions

What do radius, amount and threshold actually do?: An unsharp mask blurs a copy, subtracts it from the original and adds a scaled difference back to each RGB channel. Radius is the Gaussian standard deviation, from 0.1 to 10 pixels. Amount is 0 to 300 percent; 100 adds the difference once and 0 leaves the decoded canvas pixels unchanged. Threshold is 0 to 255 and skips a channel when its absolute difference is smaller. Defaults are radius 1.2, amount 85 and threshold 4; they are an editable example, not settings for every photo.
How do I sharpen a photo without halos?: Compare the result at the size you will use it, reduce Amount if edge rims become visible, and try a smaller Radius if the rims are broad. Threshold skips small channel differences and can reduce changes in flatter areas, but it does not guarantee that noise or halos disappear. The tool warns above amount 150. The worked examples show the same edge at amount 85 and 300 so you can compare the effect.
Can a blurry photo be fixed?: The unsharp mask can make existing edges more distinct, but it cannot recover detail lost through missed focus, movement, compression or enlargement. Stronger settings can amplify noise and artefacts. This tool does not deblur, upscale, remove noise or generate replacement detail. Use the comparison divider to judge the actual changes rather than treating a stronger edge as recovered information.
Is transparency preserved?: The unsharp operation retains the alpha values from the decoded canvas image, and its blur weights neighbouring pixels by alpha. PNG export retains that transparency. Browser decoding, colour conversion and canvas handling can affect the source data before sharpening, so this does not promise byte-identical source pixels. JPEG has no alpha; the page warns that transparency will be filled with white before saving it.
Is my photo uploaded?: No. The file is read by the page itself, decoded by your browser, drawn onto a canvas and sharpened in memory. There is no server in this and no endpoint for an image to go to, nothing about the picture is sent to analytics, and nothing about it is written into your browser's storage: the tool remembers your radius, amount and threshold between visits, and that is all it remembers.
How large an image can it sharpen, and what comes out?: Up to 30 megapixels, which covers a 6,000 by 5,000 frame. A larger file is refused in words, with the megapixel size it read and the ceiling, rather than being quietly shrunk to fit; resize it first and sharpen the smaller copy. What comes out has exactly the same pixel dimensions as what went in, because sharpening changes values and not geometry. The download is your own file name with -sharpened on the end, as a PNG, or as a JPEG written at 0.92 quality when you choose that instead.
How do I sharpen an image in Photoshop?: In current Photoshop desktop, select the image layer, convert it to a Smart Object if you want to edit the filter later, and inspect the image at 100% zoom. Choose Filter > Sharpen > Smart Sharpen. Adjust Amount and Radius, set Reduce Noise if needed, choose the appropriate Remove blur option, preview the effect and select OK. This is a Photoshop instruction, not an edit to a Photoshop document by this page; no method promises to reconstruct missing detail.
How do I sharpen an image in GIMP?: In GIMP 3, open the image and choose Filters > Enhance > Sharpen (Unsharp Mask). Adjust Radius, Amount and Threshold while previewing the result, then apply the filter. GIMP uses its own ranges and image pipeline, so do not copy this page's slider numbers as equivalent GIMP settings. This page processes a local raster image separately.
Can I sharpen PNG, JPEG, screenshots or text in a raster image?: Use a file your browser can decode, commonly PNG or JPEG, or paste a screenshot when the browser permits it. The same mask acts on existing pixel edges, including raster text; it does not recognize or replace letters. PNG can retain transparency, while JPEG uses a white background and lossy encoding. SVG/vector editing and PDF-document sharpening are separate workflows.
Is this AI sharpening or image upscaling?: It uses the stated Gaussian unsharp mask, with no inference model, generated detail or change of image dimensions. It cannot perform AI reconstruction, enlarge a picture, sharpen just a selected region, or repeat a blur/sharpen operation automatically. Radius, Amount and Threshold apply to the whole decoded image.
Can I use it on iPhone, Windows or without a watermark?: Open this page in a current browser and choose a decodable image from the device file picker. Clipboard image support varies, so use the picker if paste is unavailable. The output contains no added watermark, and the core requires no sign-up. This is a browser tool, with no installed sharpening application or access to your device photo editor.
Will sharpening leave every colour unchanged?: No. This mask changes RGB channel values to increase local edge contrast. Its alpha handling preserves decoded transparency, but it has no luminosity-only mode or colour-profile preservation guarantee. The screen comparison shows the actual decoded and processed images; it does not certify unchanged colours or print appearance.

An unsharp mask raises contrast along edges that are already in the image. It cannot recover detail the camera never recorded, so a blurred or heavily compressed photo cannot be made sharp, and a high amount produces bright halos along hard edges rather than more detail. Images up to 30 megapixels are accepted.