Fill Flash – Indoors & Out

Flash Techniques:
Fill Flash
I’m surprised at the number of advanced photographers who remain mystified by fill flash.  This powerful technique is simply the blending of two light sources during one exposure.  The primary light source is natural light and the secondary light source is your flash.  During full flash the camera is arbitrarily set at the highest synch speed, but with fill flash, simply shoot in aperture priority and let the flash do the rest.
31165_fillAperture priority is the best mode for using fill flash.  You select the appropriate aperture for the situation and let the camera decide the correct shutter speed.  Assuming the subject isn’t moving and the camera is supported on a tripod, most shutter speeds work.  Your flash can fire at any shutter speed at or below the flash synch speed.  To get started, pretend your flash is turned off and set exposure as you normally do in aperture priority.  Next, set the fill flash to automatically reduce flash output by  -1-1/2 or -2 stops.  Don’t confuse this setup with power settings that manually vary the flash output.  Manual setting will not work as intended.  You want the flash output automatically controlled at your desired setting while in aperture priority mode.  Check your owner’s manual for exact directions for your system.
D6069_fillOnce the flash is set to a substantial minus setting simply shoot as if the flash is not in use.  Fill flash has virtually no effect on the overall exposure.  The magic of fill flash is that it only affects the shadow areas of the image.  Even when set at minus two stops; fill dramatically opens up shadowed areas on cloudy days or during indoor situations.  Shadows can be quite harsh on bright sunny days; consider boosting your fill settings to -1/2 or -1 stop.  My standard setting for indoor/overcast lighting is -2 stops.  Fill light adds a beautiful catch light in the eyes of your subject whether shooting inside or out.  The idea is to blend the flash seamlessly so the subject looks completely natural and not flashed.  Simply reduce the flash exposure to a point well below the natural light exposure and shoot away like normal.  If you’re in doubt about which setting to use, it’s better to err on the side of too little flash.  At least the subject won’t look flashed.
24065_fillUnlike full flash, fill does not freeze subject motion or eliminate camera shake.  Remember, two exposures are taking place, one for the flash and one for the natural light.  If nothing moves, both exposures overlap perfectly as one.  Ghosting occurs if there is movement during the exposure.  Fill light freezes movement the instant the flash discharges, but the subject keeps moving during the time the shutter is open for the ambient light exposure.   The lag time between the flash firing and the shutter closing creates two overlapping images; one blurred and one sharp.  Fill flash won’t freeze the action of your active kids, but it can greatly improve the quality of images inside and out.  As in any normal shooting situation, make sure the shutter speed is adequate for the situation and the let the flash work it’s magic automatically.

Using Flash – The Basics

The Basics
Small portable flash units have revolutionized 35mm SLR photography, freeing us from the limitations of natural light.  Millions of amateurs own cameras with built in flash, yet flash is one of the least understood tools of photography.  Understanding just the basics of how flash works, will let you do some pretty amazing things with flash.
Special Shutter Speed_basicsFlash photography requires that you learn and work within the quirky characteristics of flash illumination.  Light from any single camera mounted flash has two inescapable characteristics.  First, light from a small light source is very harsh for portraits.  Flattering portraits are usually made with a much larger light source, so don’t expect a small flash to bath your subjects in flattering light.  Basic Theory:  From ten feet away a single flash unit is a tiny light source when the subject is as large as a person. The same flash unit ten inches from a small insect is a much larger light source.  A flash mounted in the camera hot shoe compounds the harshness of a small light source.  All built in flashes and even accessory flashes mounted in the camera hot shoe, are too close to the axis of the lens. The lighting is unflattering, often producing red eye where the subjects eyes glow like some alien life form.  Moving the flash off camera a few inches can make a noticeable improvement in lighting quality.  When using only one flash, I prefer to have it right above the lens, but elevated a few extra inches.
Inverse square law_basicsTo improve the quality of your indoor flash pictures, try bouncing light off a large white surface.  Walls and ceilings work fine as long as they are white.  Flash picks up a colorcast when bounced off colored walls and ceilings.  Bounced flash is less harsh because the light expands tremendously before reaching the ceiling where the large illuminated area is then reflected downward on the subject, creating an effect similar to that of a much larger light source.  Keep in mind that a lot of flash power or distance is lost when light is bounced.  Use a wide aperture and stay reasonably close to your subject.  TTL flash metering compensates as long as you don’t exceed the flash maximum distance range.  Bounce lighting means the light must travel further to reach the subject and power is lost due to light scattering.  If your flash is not powerful enough, kick up the cameras ISO a few stops and in effect you have a much more powerful flash.
Bounced on camera flash_basicsThe second characteristic of all light sources is governed by the laws of physics and is referred to referred to as the Inverse Square Law.  This law states that light from any single point light source diminishes according to the square of distance it travels.  In simple terms, this means the power of your flash diminishes very quickly with distance.  Logically you would think that doubling the distance to your subject would reduce the light reaching that subject by one half.  It’s much worse; light reaching the subject is reduced to only one forth.  In terms of camera adjustments, you’re loosing 2 F-stops of light when you double the distance.  The good news is that your TTL (Through-the-Lens) flash automatically compensates for variations in distance within limits of the flash range.  However, no TTL system can correct for light falloff when trying to illuminate subjects near and far in the same shot.  In practical terms this means that elements a few feet in front of a correctly exposed subject will be overexposed, and elements a few feet behind will be underexposed.  Work around this limitation by keeping subjects at roughly the same distance from the flash.  Moving closer to a subject exaggerates light falloff.  The best tactic for illuminating subjects at varying distances is to back up.  In other words, moving the flash further from the subject reduces the difference in illumination between near and far subjects.  With this basic theory, lets move on to full flash and fill flash.