I selected f/6.7 simply because under this overcast sky it kept the shutter speed at 1/180 second, and I have found that 1/180 second is a good speed to capture RAIN at with a telephoto focal length,and it was lightly raining. I wanted to be able to see the rain streaking, and to the left of the pigeon you can see a rain drop that has just splattered off the bird's back. At faster speeds,rain doesn't look like rain,and at slower speeds,droplets that have impacted get too long. I think my new sharpening routine for the 12MP in-camera JPEGs might be just a little too aggressive in this 50% reduction.