There are five main directions light comes from to create shadows. A good photo editor must know to create realistic shadows for each type.  Backlight - Light from behind the subject, casts a shadow in front of the subject. Frontlight - Light from the front of the subject, casts a shadow behind the subject. Sidelight - Light from the left or right of the subject, casts a shadow on the opposite side. Overhead light - Light from above the subject, casts a shadow directly below the subject. Upward light - Light from underneath the subject, casts a shadow upwards.