Did you know that when using your DSLR and looking through the view finder, you're looking through the lens wide open. The larger your maximum aperture, the brighter the scene infront of you will be.
The depth of field you can see is also the maximum wide open aperture too! Even if the aperture is set to f8, for example, you'll still be viewing the maximum aperture of the lens. You can preview the depth of field set in the camera with either live view mode or the depth of field preview button.