This document discusses three key photographic techniques: depth of field, shutter speed, and digital noise. Depth of field refers to how much of an image appears in focus, with shallow depth of field meaning less is in focus and deep meaning more is in focus. Shutter speed controls the length of time the camera shutter is open, with slow shutter speeds slowing motion and fast freezing it. Digital noise appears as spots or lines on an image and can be caused by various factors like scratches, dust, or glare.