Now that shot was taken from my seat with the 14-54mm f/2.8-3.5 II zoom on my Olympus E-3, an excellent walking-around lens, cranked all the way out to 54mm. With the crop factor of the Four Thirds sensor in the Oly DSLR, that's the equivalent of a 108mm lens on a full-frame camera.
I wanted to get a closer shot, so I either needed to get closer or get more focal length. Thing is, get too close to the dog with the camera and he's going to stop laying there and get up and try and see what you're up to and it blows the whole shot.
I also wanted to be able to get the shot at the camera's native ISO of 100 to minimize noise...
Fortunately, that green blur at the bottom edge of the snapshot there is my camera bag, and in that bag is my secret weapon for a situation like this: The Zuiko 150mm f/2.
Et voila!