"Wonderfully Visual" (Zooey47) - "Simple and extremely effective" (Blaxall88) - "Good just got better!" (Snaxalig). Ever wondered how depth of field at f1.4 compares to f11 - What does an exposure difference of two f-stops feel like - What makes a subject a subject. Just try it out with the flick of a finger in this interactive book by photography instructor Chris Marquardt, host of Tips from the Top Floor. PocketChris is the photography instructor in your pocket.