In an XNA 2D game, I am thinking about blurring the background slightly to increase the feeling of depth? I am already using parallax scrolling which works pretty well in terms of enhancing depth perception. However, some newer games e.g. Super Mario Bros. 2 on the Nintento 3DS additionally use a blurred background.
Admittedly, this is a pretty extreme example:
For me, the blurring visually is not very pleasing but nevertheless somewhat enhances the feeling of depth. I was wondering if there are any studies or personal experiences out there on the subject?
At the moment, the blurring is created by a HLSL pixel-shader (or GLSL though Mojoshader with MonoGame) which is parameterized by the velocity of movement (the faster the more blurred).