Vignette

Darkens or brightens the edges of the frame.

Amount is the strength – positive darkens, negative brightens. Midpoint sets how far out from the center it starts, Feather how soft the transition is.

Roundness shapes the falloff. In the middle it’s a circle. Toward the left it becomes an ellipse in the crop’s proportions, so a wide frame darkens along its long sides as well as its corners; toward the right, a rounded rectangle that follows the edges of the picture.

Lens

Chromatic Aberration is the colored fringing a lens leaves on high-contrast edges. The three color channels don’t land at quite the same size, so they drift further apart the further you go from the center – none in the middle, most in the corners. Strength is how far apart they get at the edge, Growth how quickly it builds on the way out.

Sharpness is resolving power, not blur. At 100 the lens resolves all detail in the original image; below that, fine detail is softened while edges stay where they are. Falloff lowers the lens’s resolving power toward the corners.

Distortion Amount – negative values create barrel distortion, positive values pincushion. Edge bends only the outer field, so setting it against Amount gives the moustache an anamorphic lens leaves. Size is the radius both are measured against: shrink it and the bend bites harder across the frame, grow it and the picture sits in the flat middle of the curve.