Optics and lens blur

Optics corrects what the lens did to the picture. Lens blur does the opposite: it adds a defect on purpose, because shallow depth of field is one people like.

Lens corrections

• Lens correction applies a profile for the lens that took the photo, straightening barrel or pincushion distortion and evening out corner falloff.
• Chromatic aberration removal clears the coloured fringing that shows up on high-contrast edges, with separate purple and green amounts for the two fringes that occur.
• Distortion and vignetting are manual overrides for when the profile does not go far enough, or when you want the falloff back for effect.

Lens blur

Lens blur simulates a wider aperture, throwing the background out of focus while the subject stays sharp.

• Amount — how strong the blur is.
• Bokeh — the shape out-of-focus highlights take, which is the character real lenses differ in.
• Focus distance — which depth stays sharp.
• Focus range — how deep that sharp band is. Narrow it for a dramatic effect, widen it to keep a whole subject in focus.

Lens blur is at its most convincing when there is genuine depth separation in the scene. On a flat subject shot straight on, the effect has nothing to work with and tends to look pasted on.

For blur confined to an area you draw yourself rather than by depth, use a mask instead.