The Vignette section darkens the image from the center toward the corners, like the light falloff of a lens. It is not a property of the model: it is a camera effect, applied over the finished image.

Controls

Strength: From 0 to 1. At 0 the effect is gone. Near 1 the corners go quite dark, and the center of the frame becomes the only bright region.

How to use it

Values between 0.2 and 0.4 are usually enough: they give a photographic finish without the reader noticing where it comes from. High values, like the one in the image above, are for covers and thumbnails, where the subject has to jump out.

The darkening happens before tone mapping, so it preserves the contrast of whatever survives instead of washing the image out. With a transparent background, the vignette darkens the object, not the empty space around it.