Fill Flash Demystified

How many times have you attempted to take a beautiful snapshot of your spouse or child, got the background perfectly exposed but ended up with a dark face or, even worse, a silhouette? How many times, on a perfectly sunny day, do you end up with dark or underexposed subjects? If this sounds familiar, continue reading to discover why this happens and how adapting a simple technique, called ‘fill flash’, will make this an issue of the past.

Let me first explain why this phenomenon occurs, as understanding the cause of a problem is vital to understand its solution. Usually while taking a photo, the camera ‘meters’ or decides how much light is available in a particular situation, and sets the aperture and shutter speed accordingly. Usually, today’s digital cameras do a pretty good job and accurately decide the right settings in most commonly occurring situations, but very bright or very dim light can complicate matters. If a scene has very bright background, the camera is ‘fooled’ into exposing for the brightness, and ignores the subject placed in the foreground. The bright background caused the camera to fix a very low shutter speed or narrow aperture (or both), resulting in the bright background getting properly exposed, but the foreground getting underexposed. This is the main reason for dark faces in otherwise perfect photos. If we set the camera to meter for the foreground subject, a longer shutter speed or wider aperture is chosen, which results in blown out and over-exposed background.

So, what's the method to get both the foreground subject and the background perfectly exposed? The answer is very simple: use the 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.

So, what are the common situations when you may need to use fill flash? In short, you'll want to use fill flash in every condition where the background and foreground have dissimilar lighting, but here are a few representative situations:

1. Light coming from overhead, say sunlight at noon, may cause shadows to appear on the face, below the eyes, or on one’s clothes. This is more so if the person is wearing a cap or hat.
2. If the subject is standing in a shaded area, like beneath a tree or if any kind of shadow falls on the subject’s face/body.
3. If there is more light behind the subject than in front, as in a sunset or sunrise situation.

Now comes the most important question: can fill flash be used in every situation of dissimilar lighting? The answer to this question is tricky. One has to bear in mind that flash, after all, is not natural lighting. It’s a very intense white light. Hence, if the aim is to capture natural light, fill flash should not be used. Examples are if one wants to capture the evening sunlight reflected off a surface, or if photographing self-luminescent objects like flames, say a burning candle, or embers, or any source of light less brighter than the flash itself. Fill flash, if used here, will kill the tonality of the light and produce harsh, flat images.

So, here’s a quick low-down on fill flash photography.

1. Used when foreground subject in shadow or less illuminated compared to background.
2. Set the camera to ‘Force-Flash’ or similar mode.
3. Set ‘Auto Red-eye Reduction’ or similar, to ‘Off’.
4. Make sure you’re within range of your flash unit.
5. Meter using the ‘Single spot’ or ‘X’ mode. If using an SLR camera, use TTL metering for the external flash.
6. Shoot multiple exposures, bracketing the intensity of flash, till you get the perfect exposure.
7. If the camera does not allow FEC, simply move in closer or move out farther away till you get the exposure right. You may also try zooming in or out for a similar effect.
8. Experiment! Experiment! Experiment!

Please read Understanding Flash Photography for additional tips and information on the various ways you can use flash to enhance your photography skills.