Advertisement
How the effect is built
Two things happen at once. First the whole image is blurred with a multi-pass box filter, which is a close approximation of a Gaussian and is fast enough to run on a full-resolution photo. Then an oval mask, centred on the frame, decides how much of the blurred version each pixel receives. A smoothstep curve controls the transition so there is no visible ring where the sharp region ends.
That is exactly how a lens behaves: sharp in the focal plane, progressively softer away from it. It is not subject segmentation, which is why centring your subject gives the best result.
The three controls
| Control | What it changes | Start at |
|---|---|---|
| Blur strength | Radius of the background blur. | 26 px |
| Sharp area | How much of the centre stays in focus. | 35% |
| Edge softness | How gradual the hand-off to blur is. | 30% |
Tips for a convincing result
- Centre your subject first. Crop the photo so the subject sits in the middle of the frame — the mask is oval and centred by design.
- Do not over-blur. 20–35px reads as a real lens. Beyond that it looks like a phone filter.
- Keep the sharp region a little larger than your subject. A tight mask clips hair and shoulders.
- Fix shadows first. A blur makes uneven lighting more obvious, so correct it with remove shadows from photo before blurring.
Works best on portraits, product shots and food photography — anything where the
subject is central. It is not a substitute for a real shallow-depth photo where the background needs to be
sharp at one edge and blurred at the other.
FAQ
How do I blur the background of a photo online for free?
Upload the photo, raise Blur strength until the background softens, then use
Sharp area to shrink the in-focus region around your subject. Adjust Edge softness so
the transition does not look like a ring. Download as PNG.
Does it detect my subject automatically?
No. It uses a radial mask centred on the frame, which is why it works best on portrait-style photos
where the subject is in the middle.
Why does the result look like a soft vignette?
Edge softness is too high, so the transition is gradual across the whole frame. Lower it to
make the in-focus region more defined.
Can I blur only one side of the image?
Not currently. This tool uses an oval mask centred on the photo. Crop the image so the subject sits in
the middle before uploading if you need an off-centre effect.
Related tools
Advertisement