Photographers learn to interpret photographs in that technical way because they want to understand and use that ‘language’ themselves (just as musicians learn a more technical musical language than the layman needs). Social scientists who want to work with visual materials will have to learn to approach them in this more studious and time-consuming way.
Every part of the photographic image carries some information that contributes to its total statement; the viewer’s responsibility is to see, in the most literal way, everything that is there and respond to it. To put it another way, the statement the image makes – not just what it show you, but the mood, moral evaluation and casual connections it suggest – is built up from those details. A proper ‘reading’ of a photograph sees and responds to them consciously.