DOF setting creates brighter renders...

[vijo]

I've encountered a weird problem when I try to render a scene, when I turn the DOF setting (in render settings) up above 2 the render becomes a lot brighter (metal which is otherwise grey becomes completely white) Any idea of what this could be?

[andy.engelkemier]

it's more than likely creating a bloom effect, which a camera would probably do as well. But it's hard to know without seeing an example.