This is your first paragraph.
Your camera controls its flash system, be it built-in or external, based on the selection you make from the available camera flash modes.
Depending on the camera model, you can either select a flash mode using a button on the camera body or using the flash set-up menu in the camera's main settings. These camera flash modes also control the way that the camera flash interacts with your main exposure system.
The Auto Flash Mode option automatically fires the flash whenever the light level is low for a good exposure or when the main subject is backlit. This setting is the best choice for most shooting circumstances.
This mode is designed to reduce the red eye problem you often see in photographs taken with compact cameras . It works by firing two flashes to minimize red-eye in the subject - first a pre-flash to shrink the iris, and a moment later the actual flash to expose the image. Such features do not guarantee that red eyes are eliminated but rather the chance of it happening is reduced or minimised.
There is also a downside to using a red-eye reduction mode - many subjects blink during the pre-flash, and then the second flash catches them blinking. Or sometimes subjects think that the first flash means the photo was taken and they move and the second flash fires to capture their movement on the photo.
To successfully eliminate red eye, you need an external flash that is positioned away from the axis of the camera lens. If however you do not have an external flash but only a built-in flash, the best strategies are to zoom the lens out to a wider angle, tell the subject to look directly at the camera, try to get close, or increase the overall room lighting.
On most cameras you have the option to turn red-eye reduction mode off.
The Red-Eye Reduction mode is useful when shooting portrait images but in many other situations you might want to turn it off as it does introduce a very brief delay between pressing the shutter button and capturing the image because the red-eye reduction light needs time to flash.
With the Fill-in Flash Mode, often called Flash On or Forced Flash , the flash fires every time a picture is taken even if there is enough available light to take the picture without flash.
You will select this camera flash mode when you want to filling in shadows when photographing in bright sunlight or when your subject is back or side lit. In such situations shadow areas can be so dark in the image that they show little or no detail. And when the subject is backlit or against a bright background, it can be underexposed.
Fill flash is also a good way to get accurate colour balance under unusual lighting.
Using the fill-in camera flash mode is also very useful when photographing room interiors, which may include a window and where the existing light alone leaves heavy black shadows. If possible, use a powerful flashgun in these circumstances and bounce the light off a suitable wall or surface not included in the picture. This will produce the most even fill-in effect for the scene.
In very dim lighting conditions, flash images show a well exposed foreground subject against a black background. The Slow Shutter Flash Mode is designed to minimize this problem by leaving the shutter open longer than usual to lighten the background.
This camera flash mode works by firing a short burst of flash during a longer exposure to freeze objects while still allowing them to blur. If you want to avoid the blur, you will need to use a tripod or use this effect creatively.
This mode is best used for night portraits where the flash lights up the person and the long shutter is used to record the night or city lights.
usually set on the flash, not on the camera. It works by firing the
flash a number of times at high speed to capture multiple images of the
same subject in the same photograph.
This camera flash mode is often used in sports photography for motion studies of a moving subject i.e. golf swing.
This feature is supported in some
flash units and you will use it in situations where you want to use a
shutter speed that is faster than the camera's flash sync speed. It
works by firing numerous rapid bursts of light ensuring that the entire
image is illuminated even at extremely fast shutter speeds.
The only drawback is that the feature minimizes the effective flash range so you can't be positioned as far from a subject. The higher the shutter speed you use, the closer you have to be.
Using flash can over or underexpose a subject and it is through the flash exposure compensation that you can manually control the amount of flash light cast over your subject without changing the camera's aperture or shutter speed.
This is an ideal way to balance flash and natural light when using fill flash and to correctly expose scenes or subjects that are darker or lighter than normal. It can give excellent results as it allows you to make more details visible in the shadows, while minimizing the "flatness" that can occur when full flash is used and all the shadows are removed.
The exposure compensation function often lets you vary flash exposures plus or minus 2 stops in one-third stop increments.
This feature is similar to Autoexposure Backeting. In situations where you might find it difficult to obtain a proper exposure, the flash exposure bracketing allows you to take a series of two or three consecutive pictures exposed at slightly different settings above or below the exposure recommended by the autoexposure system. The flash output changes with each image while the background exposure level remains the same.
Flash exposure lock is very similar to AutoExposure Lock and can be used to set the flash exposure for an important subject area in your image.
The feature works by firing a preflash that is used by the light metering system to calculate correct exposure for the primary subject area and the resulting flash settings are locked in. You can then recompose the scene or make exposure or focus adjustments without losing your flash exposure data.
Flash Exposure lock feature is extremely useful when the main subject is off-center or there is a strong backlighting.