In the process of learning to be a good photographer, there are several conceptual hurdles you have to pass. The first one is how to properly control the three key elements of exposure (ISO, shutter speed, aperture) and make trade-offs between image quality, motion control, and depth of field. Another, more difficult, hurdle is learning how to control light.
The strobist blog is a great resource for learning this stuff, and I was going back and reviewing one of the posts in David’s Lighting 102 series on the importance of position and distance. A formal education in photography involves learning things like the Inverse Square Law, but the general idea is this. The closer your light source is to your subject and the farther away the background, the less background you get in the picture. And furthermore, this effect isn’t linear (this is where the “square” part comes in). The effect gets more and more pronounced as you move the light source in.
Your initial thought at seeing the picture of the skeleton might be that it was taken in a dark room. In fact, it was taken in our well-lit living room in the middle of the day as you can see here.
As you can see, the light source is very close (a couple of feet) away from the subject. To avoid blasting the subject and to emit as little light as possible, I have the flash dialed down to 1/16th power. That’s more then enough light to illuminate the skeleton, but it won’t do much beyond that. Also note that the flash is direct (i.e. not diffused with something like a shoot-through umbrella or a stofen cap). The goal here is to make this thing look scary, and harsh light is good at that. Finally, the flash is off-camera and triggered with a Pocket Wizard (a little radio transmitter).
Once the flash is set, the next set of decisions are around the exposure controls. The thing to know here though is that you’ll need to shoot in Manual exposure mode. The effect being done requires virtually no light to be collected at the sensor except that which comes from the flash. If you used one of the auto-exposure modes, it would try to go for a balanced exposure that captured the background. But, we don’t want the background – so we need to take control and ignore the camera as it yells at us and tells us we’re grossly under-exposing the image. For those who care, I ended up shooting at my camera’s maximum sync speed (shutter speed of 1/250th of a second) at ISO 100 and an aperture of f/20. Without the flash, that combination of exposure controls would have resulted in a near-black picture. But the flash lights the subject and we’re good to go.
The final step was to make a slight adjustment in the image on the computer. As shot, the background isn’t completely black – but it’s pretty darn close. So, the adjustment I made on the computer was to use the Levels control (almost any photo editing program has one of these) and force anything that was close to black down to black.