Understanding Fill Flash
For an amateur or beginner photographer, it may seem very confusing to be using the flash in bright daylight. Many point-and-shoot digital cameras might even refuse to do that when used in the ‘Auto’ mode. But the logic here is quite simple - the dark faces are primarily due to insufficient exposure. A flash throws just about enough light on the foreground subject, making it temporarily comparably bright as the background, and thus getting it properly exposed. So, the flash basically ‘fills’ light in the relatively darker foreground, and hence this technique is known as ‘Fill Flash’.
Many digital cameras allow a person to control intensity of the flash, a setting known as ‘Flash Exposure Compensation’ (FEC). Changing this setting increases or decreases the intensity of the flash. If your camera offers this setting, it's highly recommended to use it to give a more natural feel to the flash filled area. So, what are the parameters to be kept in mind while altering FEC? Firstly, the distance of the subject from the camera. Next, the lighting conditions, viz., angle and intensity of light falling on or behind the subject. One has to take care that if he is quite close to the subject, the flash intensity should be set a stop or so less, so that the subject is not overexposed and vice versa, if the subject is relatively afar. An average digital camera has a flash range of only up to 10 feet. So, if the subject is beyond the range of your flash unit, this technique may not work.
Another consideration, as mentioned earlier, is that quite a few digital cameras do not allow flash to fire if set in ‘Auto’ mode in bright conditions. In such cases, it may be necessary to set it to ‘Force Flash’ mode. This mode is usually represented by an icon similar to a bolt of lightning.