Vignette

The word comes from French: vignette, a diminutive of vigne, the vine — once the name for vine-leaf ornaments in the margins of books. Later it meant a portrait fading softly into its background, and in photography a darkening towards the edges of the frame. Lenses do it on their own; photographers and designers do it on purpose, to hold the eye in the centre.

How it works

In a real lens the fall-off has several causes. Even a perfect lens obeys the cos⁴ law: light heading for the edge of the frame at an angle θ travels further (cos²θ by the inverse-square law), strikes the film or sensor obliquely (another cos θ) and sees the lens pupil squashed into an ellipse (one more cos θ). At θ = 30° that leaves 56% of the light, at 45° just 25% — two stops down. Add vignetting proper, where lens rims clip oblique bundles and turn edge bokeh into cat's eyes, plus hoods and filters that cut the corners.

The effect is simpler and more obedient. Distance from the centre is measured in an ellipse that “Roundness” morphs from an oval fitted to the frame into a circle; the darkening rises smoothly from “Size” to “Size” plus “Softness”. The picture is blended towards black, white or a palette colour, with half a level of noise mixed into the fall-off so no 8-bit steps show.

A bit of history

Joseph Petzval's portrait lens of 1840 was the first fast one, with a sharp centre and dark, swirling edges; copies are still made for that look. Victorian photographers printed portraits through masks with a soft oval cut-out, so faces floated in white mist. The Soviet LOMO Compact-Automat (1984), with its heavy vignette, became the icon of 1990s Lomography, and the first Instagram filters (2010) made the vignette shorthand for “analogue”.

What to tweak

• An “Amount” of 0.2–0.4 with a large “Softness” is an invisible vignette that simply holds the eye; viewers notice it only when it is gone.
• “Roundness” 1 with a small “Size” is a telescope or a door peephole.
• “Fade to” set to “light” is a Victorian portrait in a white oval; “colour” with the document background as its “Colour” dissolves the picture into the page.
• “Centre X” and “Centre Y” move the pool of light onto the main motif.
• A vignette frames centred compositions best — Kaleidoscope, Phyllotaxis, Guilloché and spirograph, Chladni figures. It breaks seamlessness, so tile mode leaves it out.