This image illustrates depth of field settings in Blender 3D. The center cube is the object of focus, leaving the background and foreground blurry. Pretty simple stuff in photography. In Blender 3D, however, we are able to control both the location and the depth of the effect. 

An interesting result of camera technology is the effect known as "bokeh," as illustrated above. You can see that distant, out of focus lights have formed a triangular blur. In a physical camera, the shape of the bokeh blur is determined by the number of blades the lens uses to control aperture. In Blender, we can simply set the number of virtual blades our camera uses, easily simulating bokeh effect. In this photo, the blade count was set to 3, thus the triangular blur. 

The pentagonal blur here is thanks to a 5 bladed aperture. (Note: the noise in this image is significantly reduced as compared to the above images because it was rendered at a much higher sampling rate. This is unrelated to the change in aperture.)

This image was rendered with a 3 bladed aperture, with the addition of a slightly-frosted glass material, and a roughed metal ball. All this was rendered at a slightly higher aperture width overall, and at 5000 samples. (Fun fact: this was highest sample rate I have ever rendered an image at! Hurrah for capable computers.)

With a few, basic, post processing effects applied, this is the final result. I only needed an RBG Curve node and a Glare node in the Blender compositor to produce a stylelized, high-key lighting effect.

 

Many thanks to Gleb Alexandrov for a tutorial focusing on the bokeh effect (http://youtu.be/aKefFf0k5yE) and another phenomenal tutorial on the Blender Compositor from Andrew Price (http://youtu.be/fWcCkQ3943Y).