Softness is an important quality of light and depends on the relative size of the light source. The larger the light source appears, the softer the light. For example the sun on a sunny day is a hard light source, but a cloudy sky and a northern window are sources of soft light. Hard light results in harsh shadows and soft light gives diffused shadows.
For the first three photographs I underexposed the ambient slightly and used a soft light on the subjects – a flash in a 60″ (150 cm) white shoot-through umbrella. The photographic umbrella, positioned as close to the subject as possible (in this case camera left and above, just outside of the frame), increases the size of the light source and softens the light significantly. In a way it emulates a northern window.
This soft light blended well with the light diffused by the canopies of the trees, and there are no harsh shadows. Soft light partly fills in its own shadows (and often appears to wrap around the subject).
Soft light can be achieved in many other ways – with a softbox (like in this photo shoot) or by bouncing the tilted flash from a large surface (like in this wedding shoot). These modifiers and techniques allow to shape and control the light.
For the below image I used a hard light source – a flash with a 7″ (18 cm) parabolic reflector, positioned camera right and above the subjects, with a 20° grid to constrain the light. The flash was relatively far from the subjects and the shadows are harsh.
These two light types – soft light and hard light – give very different looks. None is good or bad per se and both can be used effectively. Typically soft light is more flattering for portraits and hard light can define the subject better, bring out the details, and may create more interest by casting shadows.
One of my favorite light sources is a Beauty Dish. It combines the characteristics of soft light and of hard light and gives a unique look. I used it in the Overpowering the Sun shoot.Soft Light, Hard Light