Flash Basics

Have you ever captured an amazing image and found that, no matter what you did, you just couldn’t repeat it? Perhaps certain conditions, such as the sun shifting or a cloud passing, change the shooting environment. There’s nothing wrong with going auto everything to capture everyday images. However, if you want any kind of consistency in your photography, as well as the confidence to walk into any scenario and know how to set up your speedlight, you have to understand the principles at work. So, grab some caffeine and read on to discover what these principles are.

Achieving proper exposures

To determine the proper settings for your camera and flash to achieve a good exposure, you might want to remember this simple equation: GN/D = A. This equation contains the three most important parts of flash exposure: Guide Number (GN), Distance (D), and Aperture (A). You may, at this point, be wondering about shutter speed. Actually, shutter speed doesn’t play a role in the flash exposure — it’s a bit like Robin is to Batman — but it does come into play. I explain its role later in this chapter.