Hello, people. I'm getting very interested in the technical side photography lately, and one aspect that I absolutely would like to fully understand is: What actually happens inside my SLR? (I'm, well, old school and I shoot with film, if that matters) How does the light create a image, how does it reach the film, what happens to the light inside the lens, why is my depth of field low with a big aperture, all those things...I guess it will have a lot to do with optics? Anyway, I would like to know if you can recommend me a book that talks optics on a photographic level, if you know what I mean. I'm not necessarily interested in a full-blown course on optics, but rather how the principles influence us as photographers. Thank you for any tips.