How to blur the background of a photo

Two very different reasons to blur a background: to make a subject stand out, and to hide where you were. The same tool handles both — the difference is how far you push it.

Why Portrait mode can't fix an old photo

Portrait mode builds a depth map while the picture is taken, using the camera system to estimate how far away each part of the scene is. That data is captured at the moment of the shot. A photo taken in the normal camera mode has no depth map, so Portrait mode cannot be applied to it afterwards — the information simply is not in the file.

What works instead is subject masking: analysing the image itself to work out which pixels belong to the main subject and which belong to everything else. Modern iPhones do this on device, and it is the same technology behind lifting a subject out of a photo with a long press in the Photos app.

How subject detection works in practice

In Blur Photo the Background tool runs Apple's Vision framework to generate a foreground mask, then blurs everything outside it. Three controls matter:

• Strength. A light blur suggests depth and keeps the setting readable. A heavy blur removes the setting entirely, which is what you want if the background is the thing you are hiding.
• Invert. Swaps which side is blurred. Useful when you want the person obscured and the scene visible — or when detection picked the wrong subject.
• Refine brush. Paint to add to the blurred area or erase to pull it back. This is how you fix hair, thin objects and cluttered edges, which are where every automatic mask struggles.

Getting a clean edge

Masks fail in predictable places. Hair against a busy background, glasses, thin railings, an arm extended towards the camera, and two people standing close together are all common problems. A few things help:

1. Zoom in before refining. At fit-to-screen size you cannot see the edge you are correcting.
2. Use a smaller brush along edges and a large one for open areas.
3. Do not chase perfection on hair. A slightly soft transition reads as depth of field; a hard, surgical cutout looks fake.
4. If the mask is badly wrong, invert it — sometimes the detector found the right shape and assigned it the wrong side.

Blurring a background for privacy

If the goal is to hide a location rather than flatter a subject, treat it as a redaction rather than a photographic effect:

• Push the strength high. A recognisable shopfront or street sign at a gentle blur is still recognisable.
• Check the edges of the frame. Automatic masks concentrate on the subject; a corner of a building or a house number can survive at the margins.
• Blur any screens, reflections and documents separately with the Object tool — they are foreground, so a background blur will not touch them.
• Remove the location metadata. Blur Photo strips GPS from exports by default.

Which tool for which job

Background blur is for everything behind a subject. To hide one specific thing — a licence plate, a laptop screen, a poster — use an object brush instead; it is faster and far more precise than asking a subject mask to do it. For people, see how to blur faces.

Questions people ask