Talking about Strobes

by John Siskin

One problem with teaching lighting is that terminology is fuzzy. Flash used to mean a one use bulb, like a flash cube, this technology finally died in the seventies. We should call everything else strobes, but we don’t, which is confusing. Strobes make light by sending a spark through a tube filled with xenon gas; the light on all strobes is pretty much the same. What is different is the amount of light and the control systems for using the light. Manual strobes have different power levels, set by the operator, and a way to trigger the strobe when the shutter is open. These are the most powerful strobes available. The original automatic strobes used a device called a thrysistor to match the amount of light they delivered to a specified amount. The result of this is that the operator would set a certain aperture, specified by the strobe, on the lens. The strobe would keep the light constant as the photographer moved closer and further from the subject. This was a big advantage in on camera strobes. Finally we got to dedicated strobes. In the beginning these were automatic strobes that set the camera to the right aperture without the photographer having to do anything. This wasn’t much of a step forward; the light control was still done by the strobe. Current dedicated strobes are much more sophisticated, they use a light sensor in the camera body, this is called TTL metering. There are two types of photography that benefit tremendously from this technology: macro/micro work and flash fill outdoors. Flash fill is using a strobe to add light to an out door picture. This is usually done to add sparkle to the highlights in the face and eyes and to open up the shadows in the face. It can really make an outdoor picture much better. The ability to do flash fill automatically is a tremendous advantage of the TTL flash units.

When you use more than one strobe to light a shot they will work together manually. A device called a slave will trigger one strobe when another goes off. Most strobe systems will not let you use a second strobe automatically since this requires much more information to be exchanged between the strobes and the camera. This information is exchanged easily with a strobe that is mounted on the camera, but requires sophisticated radio technology to accomplish with a remote strobe. Of course you can often position a remote strobe so that the light doesn’t change the exposure in critical areas. Since we have proof images available on digital cameras it is not that difficult to set up several lights in a shot because we can see what we are doing almost instantly. This makes it much easier for the photographer to control the light in the studio or in the field.