Flash 101

There are basically two types of flash available for digital cameras: the flash that is built into almost all cameras (many professional-level dSLR cameras don’t have a built-in flash), and more powerful and versatile accessory units that mount on top of the camera. Both types of flash have their uses and their advantages, and I use both regularly. Accessory flashes are more powerful and more versatile, and I talk more about when it’s time to think about owning an accessory flash unit later in the chapter. For many applications, though, your built-in flash is quite a handy tool because it lets you bring adequate light to any subject, regardless of how much light exists in the scene naturally.

TTL flash

Virtually all flash units (both built-in and accessory units) are designed to provide completely automatic TTL, or Through-the-Lens, exposure, and it’s an extremely accurate system. As you no doubt recall from Chapter 3, TTL exposure works by measuring the light at the plane of the sensor. That is exactly where and how flash exposure is measured, but with a slightly more complicated technical scenario (one that fortunately happens without you having to do much of anything other than turning on the flash — and even that is often handled automatically).