Hover over image and have surrounding images darken

[DavidC]

For clarification: I'm not asking how to darken an image when you hover over it. I'm wondering how to make other images surrounding the image your cursor is over darken.Here is an example: http://www.b-reel.com/When you hover over the big category images, the surrounding images darken, but the hovered image remains the same.Any input would be appreciated. Thank you!