This book is really great! It is what I was looking for: a simple way to explain some concepts myself blurred (focal length, aperture ...). Reading is very fluid, diagrams or pictures explain them and then say, this book is a great help for the choice of lens, it shows by theme (portrait, landscape, animal ...), the objectives would best and why. Regarding the objectives presented, other information is: the price (new, used), weight, length, filter diameter, distance focus ... and a detailed paragraph of the goal. I therefore recommend this book to anyone interested in learning about these features. Now I ordered the objectives, and there will have to test them ;-)