D] Depth of field
Anumber of factors affect the depth of field, or how sharp an image is from front to back. Small apertures increase the depth of field and large ones decrease it. Depth of field is also affected by the distance at which you focus. The closer you focus, the narrower the depth of field becomes. Longer lenses emphasise this effect, as their narrower viewing angle means that any background blur appears larger in the frame. For maximum depth of field, use wider lenses, avoid focusing on the nearest object and choose smaller apertures.
Depth of field is shallower with larger apertures – in this example, only the foreground is sharp with the aperture set to f/5.6.