Why use a vignette?

Why use a vignette?

In this image of Jake and Elwood the Zombie Blues Brothers I decided to add some dark vignette because the background of the image is cluttered and detracted from the portrait. When you're out in public making portraits, whether they be of cosplayers like these two or street candids you still try to compose the image well and avoid trees or poles growing out of heads and things like that but your time is limited. If you move around much for a better angle you'll be noticed and any immediate candidacy of the moment will be lost.

You can apply a dark oval shaped vignette centred on the faces in post to soften the background and encourage the eye into the foreground faces.

It's really easy to get carried away with vignettes, they were all the rage for a while with cardboard matting of prints but died out as people wanted to see more. Today they're around as a digital post production aid to fix our compositional blunders or to just draw the eye towards your subject as it is naturally drawn to the brightest area of the image.