This image was done with Maya 5.
I simulated a Macro setting; the yellow orb in the middle of the image is located 11.3 cm from the camera plane.

Using an aperture of 4.65 resulted in a very shallow DOF, making the image look much more realistic (in my humble opinion) then with unlimited DOF (as would be the standard for a rendering).

For the technically interested:

I set up a nice auto-focus for an animation sequence using these settings:

I used the distance tool to measure the distance between camera and yellow orb - in order to focus on the yellow orb.

I then connected camerashape.focusDistance with distanceDimensionShape1.distance.

Then, I parented the first locator of the distance tool to the camera; the second locator of the distance tool was parented to the yellow orb.

As a result, no matter how the camera moves, or how the distance to the yellow orb is, it will always be in focus.

The image was done without raytracing and took about 30 seconds to render on my olden 1.2 GHz Athlon, using a 1280x768 resolution.