Keep the middle of a photo sharp and blur a frame around it, as a rectangle, circle or oval, with control over width, blur, feather and falloff.
Makes a blurred copy of the whole picture and blends it back over the original according to a mask. Inside the mask the sharp original shows; in the frame the blurred copy shows; between them the feather setting draws a soft ramp. The mask can be a rectangle that follows the edges, a circle, or an ellipse that matches the picture's proportions. The blur itself is a Gaussian blur of the radius you set, so it looks like a lens out of focus rather than a smear.
A 2048 × 1365 landscape with a cluttered foreground: Strong focus (circle, 35 percent frame, 30 px blur, 60 percent feather) keeps a 1330 px disc in the middle crisp and dissolves the edges, drawing the eye to the hut in the centre. For a 1080 × 1080 Instagram portrait, Portrait glow with the blur lowered to 12 px softens hair and shoulders while the face, which sits inside the 760 × 760 oval, stays sharp. Compare in the preview shows exactly where the transition falls.
It is the quickest way to fake shallow depth of field on a phone photo where everything is in focus, to calm a busy background behind a product, or to make a soft-edged hero image that text can sit on. Use Tilt-Shift Effect instead when the sharp region should be a horizontal band, and Blur Image when the whole picture, or a hand-drawn region, needs blurring. It is not a substitute for real subject isolation: anything in the centre of the frame stays sharp whether it is the subject or not.
The presets set all five values at once and are a good starting point. Frame width is how far the blur reaches in from the edge, as a percentage of the shorter side. Blur is the radius in pixels. Feather widens the ramp between sharp and blurred; 0 is a hard line. Even blurs only the frame, Radial adds a vignette-shaped ramp so corners are blurrier than the edges of the frame, and Linear is a gentler straight ramp from the centre. Batch mode applies the same frame to a whole set of images.
How is this different from a vignette? A vignette darkens the edges; this blurs them and leaves the brightness alone. The Radial falloff adds a blur ramp that behaves like a vignette in shape, and the two tools stack well: blur the frame here, then darken it slightly with Vignette Effect.
Why is the centre also a little blurred? Radial falloff blurs everything by a small amount that grows towards the corners, on top of the frame. Switch to Even if the centre must stay pixel-sharp.
Does the image size change? Not with Canvas set to Original: the frame is painted inside the existing pixels, so a 1080 × 1080 file stays 1080 × 1080. Pick a canvas shape such as 1:1, 4:5 or 9:16 to place the whole photo on a blurred copy of itself at that shape instead, the usual way to post a wide photo to Instagram without cropping.
What blur value should I use? About one percent of the shorter side hides detail without turning the frame into a colour wash: 10 px on a 1000 px image, 25 to 30 px on a 3000 px photo. Go higher for a pure colour halo.