Here's a very common single-strobe setup. This particular example was created to demonstrate how lighting contrast and the effects of lighting fall-off are tied to the placement of the light source. The lighting consists of a strobe, a black-backed satin umbrella with diffusion cover, and a white reflector panel.
Example 1.3a (Close)
Example 1.3b (Far)
The Lighting Setup
This lighting example is actually two examples within one. The somewhat different look of these two portraits arises purely from a change in position of the main light. The subject, camera, and reflector remain in the same positions. Example 1.3a shows the affect of bringing the main source in close and example 1.3b, the result with the source back considerably. The lighting setup is shown to the right of each example. A 46" satin umbrella with a diffusion cover (Photek Softlighter) is fitted to a monolight and fill lighting is supplied by a 42"X42" frame covered with white fabric.
Applications and Variations
This is a very simple lighting that works for a lot of applications, from headshots to full-body images. By varying the positions of the light and reflector, this setup can produce a variety of looks. For tight headshots, you might want to consider using a somewhat smaller main source and smaller reflector as well. For full-body shots, the bigger the reflector the better. White reflectors, though less efficient than silvered ones, generally give a more even fill light and are my preference for full-body shots.
A Principle and a Seeming Contradiction
One of the first principles that you'll encounter in a lighting text is that the larger and closer the light source, the softer the lighting will appear. This occurs because the light from the large source "wraps" into the shadows creating softer, gentler gradations from highlight to shadow. In addition, the larger source creates larger and less intense specular highlights, further adding to the sense of softness. So, if this is so, why does the image with the light in close seem somewhat less soft?
The Importance of Fall-off and Lighting Contrast
More than anything else, these two portrait examples show how the rate of light intensity fall-off affects the lighting contrast and look of an image. Most portrait lighting sources experience a fall-off rate roughly equal to the inverse square of the distance from the source. Lighting modifiers such as grids, and optical spot lights are exceptions. One consequence of this law is that the fall-off rate will be most pronounced nearest the source. This is shown in several ways in these examples. First, you can see a noticeable difference in the whiteness of the backgrounds in the two images. In the image with the source further back, the difference in light intensity between the face and background is noticeably less than with the light in close. As a result, the background appears whiter. A second manifestation can be seen at the face. With the light in close, there is more lighting contrast across the face. This results from both greater fall-off from the source and less relative fill illumination from the white cloth reflector and stray studio light.
In the Final Analysis
When using large diffused sources, you can modulate the "pop" and softness of your light by moving the light in and out. A light placed in too close will result in excessive lighting contrast, and one placed too far away will flatten the light while hardening the shadow edges. Many photographers suggest placing a diffused, planar source (softbox, octabox, or diffusion panel) at a distance equal to the diameter of the source's diffuser. This is a good place to start.