Tilt-Shift / Miniature Effect

The miniature-faking effect: a sharp band across the frame with everything above and below it thrown out of focus, which reads as a photograph of a model because that is the depth of field a macro lens gives. Set the band's position and width, the width of the falloff, the blur radius and a saturation boost, in either orientation, with an optional overlay showing where the band sits. Images larger than 1400 px on the longest side are scaled to that first.

What it actually does is render the picture twice — once sharp, once blurred at a single radius — and cross-fade between them per pixel, with the mix ramping linearly from sharp to fully blurred across the falloff. That is the honest limit of the effect: real defocus keeps getting stronger the further you go from the plane of focus, whereas here everything past band-plus-falloff is blurred by exactly the same amount. On a picture with a lot of depth, the far background will look no softer than the middle distance, which is the tell.

Two details of the compositing are worth knowing if the result looks off. The mix happens on gamma-encoded sRGB bytes, so the transition band comes out darker than physics would put it — averaging 0 and 255 gives the byte 128, which carries only 21.6% of the light, where a correct blend in linear light would land at 188. And the saturation boost, which applies only in the sharp zone and fades out with the blur, pivots on the Rec.601 luma weights: for pure green that grey point sits at 150 where the Rec.709 weights matching sRGB give 182, so greens shift more than a colour-managed editor would move them.

Finally, the output is fully opaque by construction. A transparent PNG will come back with those regions black, and a half-transparent pixel comes back at full strength, so this is a tool for photographs rather than for artwork with an alpha channel.