There was a lot of picture taking going on today, and considering it being a noteable passion of mine, I figured it's a good thing to ponder the physics of.
Photography is derived from the greek words "photos" meaning light, and "graphos" meaning writing. Writing with light. Aptly named, as light is the largest component of any good photograph. Every camera has exposures and f-stops that corollate with apperatures and shutterspeeds. Each of these are tools to control how much light is allowed to be exposed on the film or SD card. I don't think I know enough about SD cards to be able to confidently say how they work, but I'm sure they're incredibly similar to film, which I know more about.
Flims starts out as a sheet of chemically soaked material. These chemicals are designed to interact with light. The lense focuses and directs light from the outside world onto the film, where the reaction (once developed) takes place to mirror the image. This works for both black and white as well as color flim. Everything we see is simply a reflection of light, be it brightness and darkness or any shade of color.
There's really an incredible amount of physics involved in photography. In fact, a lot of physics takes effect in simply staging and setting up pictures (diffusing light, velocities, the speed of light, reflections ect), however I won't get to into that. When you know as much as I do about photography, talking about everything you can do with it can take more time than anyone would care to read, particularly when you're looking at all the physics behind it as well!