Looks like an easy shot, right? Take the dog out in the late day sun with some sun-lit green grass and some darker woods behind it. Then have her sit and look at you.
Well, that sounds good until you get a camera-shy dog. Right. Figures that a photographer's dog is indeed camera-shy. A lens aimed toward her gives her a strong desire to turn her head. Thus, this picture was not as easy to get as it appears to have been.
The good news is that a 300mm f/2.8 lens can capture a really nice portrait of animals – and people too.