In addition to above books mentioned ,I would also recommend Basic Photographic Materials And Processes By Nanette Salvaggio.. I Just Glanced The Whole Book , It has very good and deep explanations about many things- Light , Exposure , Optics ,Sensitometry, Color , Tone Reproduction , Filters Etc.. If u want to get strong in theoretical part i highly recommend this book...Rather Than Other Books Which explains only the practical part we need ,this book explains everything with deep science behind every aspects of Photographic materials .. But though some dragging unwanted explanations are also there in this which we need to skip.. But Overall a great book With lots of information . Thank You, Sundar Raghavan.