Strobist Lighting 102: Exercise 1.2

Continuing my Strobist Lighting 102 exercises. This exercise was intended to show that by keeping the angle of light the same and moving the light closer or further away, one can have control over the differential between light on the subject and light on other objects in the scene (like the background). The strobist guys call this "lighting depth of field." It's related to that "inverse square law of light" thing that basically says that the closer you are to the light source, the more powerful the light.

In these photos, the doll is approximately 4ft in front of a sheet of studio white paper. I started with a single White Lightning studio strobe at approximate 6 inches from doll. Turned down power all the way and metered f/25. Took shot. I then moved the light to approx 2 ft, then 4 ft, then 6 ft from doll. Each time I increased the light until I metered f/25 on the doll. The room I was in is narrow, couldn't maintain the exact angle of light in each shot. You'll notice the angle decrease somewhat as the light was pulled back.

The resulting shots can be seen above, starting in the upper left and moving around the diagram counter-clockwise. Note that in the first shot (closest light) the doll is illuminated but the background is dark. The light is closer to the doll than the background, thus the falloff in light is much more dramatic over that great distance. As you pull the light away and increase illumination, the ratio between light-to-doll and light-to-background becomes more and more even, therefore the illumination of the scene becomes more even.

All shots were Canon 5D, f/25, 1/200s, ISO 100, 350 mm on a 100-400mm lens. This was great exercise. Helped me to develop a better sense of how distance of the light to various objects in the scene really impacts the light falloff.

Below shows the approximate setup. The doll is closer to the background than it was for the actual shots above.