Creative Lighting Solutions - The Slave Flash Unit
by A.B. Russell
eBay Staff Member

If you've been reading since I began writing, I've told you about this before. If not, though, it's something that is very helpful for many people, and I felt it was worth reviewing.

Up until now, our discussions about lighting have centered on using either tungsten, florescent or daylight for your shoots. While these are good sources of light, there is something that may work better for you without a rather large investment (at least not all at once).

I'm talking about relatively small slave flash units, the kind that will screw into an ordinary household light socket. These aren't tremendously powerful alone, but when you put two or four of them together, you can get a rather respectable amount of light.

These units vary in cost; mine cost $40.00 apiece. I have four, and use them for different purposes, depending on what I'm shooting. If I'm shooting items for eBay, I could use them all together and the light I would have would be equal to many large professional flash units, the cheapest of these costing at least $500.

Keep in mind that every time you double the number of lights (assuming they generate the same amount of light each), you should close the aperture down one f-stop. That means if you place a single flash so that it's firing through a cloth diffuser and the f-stop required for correct exposure is 5.6, then two units would require f 8, and four would require f 11. It's not impossible to put enough of these units together to use your smallest stop, whether that's f 16, f 22 or f32.

Exposure with these can be more difficult, but not impossible. If you're using film and a single flash, start with the nearest f-stop to the guide number supplied with the flash, divided by 10. If that's 90, for instance, use f 8. If it's closer to 110, use f 11, and so on. Then bracket, increasing your exposure by half a stop for a couple of stops, then going to smaller apertures for two stops. Somewhere in there you will have a near perfect exposure.

Using digital can be even easier unless your camera isn't able to use external flash. With that type of camera it may be better to continue to use tungsten or florescent light.

The main advantage to using these types of lights is that you can use a much faster shutter speed with flash than with other light sources. Because of this, camera motion is generally minimized to the point where it's not detectable in the final image The downside of using these for lighting is that you may have trouble predicting what the light will do in the final image. That, though, isn't impossible either. Perhaps we'll share that next time.