If the lighting in a scene is nonuniform or if there are shadows, the lightning will, in general, appear more nonuniform and the shadows darker in the picture than in the original scene. This is purely a visual effect having nothing to do with the photographic process as such.
Photography may be defined as one link in a chain of communication by which changes in radiant energy at one place are made to produce effects at another at any desired time interval after they have occurred.
It seems to be a more or less universal human trait to give everything we see a name. Whenever we run into something we assign it to some known class that is familiar to us and proceed to think of it as related to that class. Photographs are no exception in this regard.
Pictures are often made for no other reason than that the act demonstrates the power of the photographer over time, the partial fulfillment of a deeply rooted wish.
Photography is today one of the most powerful known means of communication. It is, above all else, a descriptive medium, one which in a single picture can give certain kinds of description in a way that is wholly beyond the power of words. Ease of description in fact is not only photography’s greatest asset; it is also its own worst enemy. Because photographs carry such tremendous conviction, produce such a feeling that one was present when they were made, it is difficult even for the expert to bear in mind that they seldom look much alike the things photographed.