With beginner-level digital cameras, flash units are built into the camera, and they usually fire automatically whenever the camera needs additional light. Beginning photographers usually can change the flash settings through the digital camera's menu, including turning off the flash completely. Small, built-in flash units on beginner cameras can increase the possibility of having a redeye effect in a digital image.
With advanced digital cameras, photographers have more control over the flash, including when the flash fires and how much light the flash adds. Flash units are larger, more powerful, and can be removed with advanced models.
The quality and power of the flash unit helps determine its effectiveness in improving photo quality. Small flash units usually only work well over a distance of several feet, for example.
When a digital camera is using an autofocus feature and a flash is required, you might see the camera fire at least two flashes. The first flash attempts to give the camera enough light to use autofocus, while the second flash is the actual flash used to take the photograph.
The term "flash" also can refer to flash memory, although the two parts of the digital camera are not related.