Depth of field is the near-to-far sharpness in a picture. If both foreground and distant objects are sharp, there’s lot’s of depth of field. If only the subject is sharp and the foreground and background are blurred, it’s shallow depth of field. Both are fine, depending on the effect you’re trying to achieve in your picture. Depth of field is affected by the lens focal length (longer focal lengths produce shallower depth of field), the lens aperture (wider apertures produce shallower depth of field) and focus distance – the closer your subject the shallower the depth of field. Shallow depth of field can product attractive background blur in portrait shots, for example. This is often referred to as ‘bokeh’, though bokeh is actually something slightly different.