Contrst is one of the most significant term in photography be it film or digital. In terms of lighting, it refers to the luminance range of the subject being photographed. This is the difference between the amount of light reflected from the brightest part and the amount of light reflected from the darlkest part in the photograph. Or the difference in the brightest and the darkest parts of the photograph. Contrast in this respect is measured as a difference in f-stops between the apertures of the darkest shadow with detail and the brightest highlight with detail. sometimes for a dramatic effect, brightest or the darkest part or both may be without detail or have no tones between them. A range of about 10 f stops would mean a high contrst image with a large luminance range. A low contrast image on the other hand would have just about a three f-stop difference.
Sometimes the scene itself contains a lot of contrast. Being lit by natural light which could be direct sunlight leading to long deep shadows, you cant really reduce the contrst by any artifitial means. (you may add a reflector in conrolled situations) These may not appear very noticeable in wide shots. And also the shadows can be creatively sued to enhance the over all composition of the photograph. Its always better to lose detail in the shadows compared to losing detail in the brighter tones as washed out tones do not look very appealing in the photograph unless they occupy a very small insignificant area or a highlight. whats important is the brightness and the tonality of the visually important areas of the photograph. remmember, we notice the brightest part in a photograph before we look at the darker tones. In such situations where you cannot handle detail in both the brighter and teh darker tones its better to let go the detail in the darker and shadow areas.
Contrast due to lighting
Digitaly added contrast