This photo was shot through glass at maximum zoom, but still required a little cropping after the fact. I was able to use a narrower aperture to make it easier in case the squirrel didn't stay in a narrow window of focus, because there were no other elements inside that field- all other visual elements were far enough away to be out of focus even at the higher aperture. I used a higher ISO to create a grainy haze on the background, but not too high to keep the squirrels coat crisp.