A better name for this feature should have been ‘vignette removal’ but since the marketing department does not want to admit that their lenses vignette, they decided to use a more sophisticated name.

Basically, when enabled, it uses hardware algorithm to compensate for the underexposure in the corners.

There is a debate among video shooters if they should or not use the feature. While fixing vignettes is easy to do in post-production with still images shot in RAW format, the compressed format of video makes it much harder to do. On the other hand, letting the camera CPU decides how the image should be fixed can create issues in some special cases.

Note regarding stills

If you are shooting JPEG and activate the feature, the correction will be automatically applied. If you are shooting RAW, the file will store in its metadata that you requested the correction but it will only be applied if you use a RAW interpreter that can process this metadata, such as Canon Digital Photo Professional.

What I do

I keep it off for both stills and video and use L lenses to minimize vignetting.

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planetMitch

chief astronomer at planet5D LLC
Mitch "planetMitch" Aunger is the creator and mastermind behind planet5D.com — which covers every aspect of HDSLR cameras (and a whole lot of other cameras as well). A lover of photography since his early days, he graduated to selling stock photos to make a little bit of spare cash. It wasn’t much, but it allowed him to upgrade to better cameras as well as computers, and it wasn’t taking money away from feeding his family.
He loves the stories that the still image can tell. In the summer of 2008, he read a story written by Arnold Kim called “I Quit My Job” — Arn is the owner of macrumors.com. He started macrumors in 2000 as a hobby, and by 2008 he was making more money with the site than he was on his day job, so he quit. The surprise to the story is that he was a doctor making more than six figures! Right then and there, planetMitch dreamed about doing the same thing.
September 2008 rolled around, and Canon announced this new version of the incredible 5D — the Canon EOS 5D Mark II. It was the first Canon DSLR to shoot full HD video and the earth moved! (It really was a huge deal in the photography world.) planetMitch knew if there was ever a chance to ride a wave of something he was really passionate about, this was it — and the blog at planet5D.com was born. It is now one of the most popular HDSLR blogs on the planet, and he is making a full-time living from blogging. He couldn’t be happier!
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