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The Secrets of Effective Fill Flash Techniques
(by Les Voorhis)

Like many photographers I spent years looking for ways to improve my photographs. What was it that made the photos I saw in magazines and calendars so much better than the images I was making. How were other photographers able to control the lighting of their subject so effectively? How can they keep detail in the highlights and in the shadows?

As time went by and my skills improved, some things became obvious. The photographers that I admired used many different techniques to make their photographs stand out from the rest. Their primary strength was the time of day that their images were taken. Most of the stronger images were taken in what photographers call the "sweet hours" surrounding daybreak and dusk. It is during this time of the day that the light is of such a quality that allows images to carry a wide range of tones and still show detail in shadowed areas as well as the highlight areas. In contrast were images that were not taken at the "best" time of day or in the "best" conditions, but the photographers were able to balance the ambient light to give the image a more pleasing tonal range. This was accomplished with a variety of methods, but primarily with the use of fill-flash.

At first, fill-flash seemed a little intimidating. Part of this is due to the fact that it is impossible to see the results of the flash until the film has been processed. This, combined with the difficulty of calculating the correct flash exposure, had kept fill-flash out of my reach for many years. With the advent of newer electronic cameras and Through-the-Lens (TTL) flash exposure, fill flash has been greatly simplified and is now within the grasp of every photographer. Those willing to do a little experimenting and learn to "pre-see" how the flash will illuminate a given subject can greatly increase the control over their images.

Most hot-shoe mounted flash units emit a light roughly daylight balanced or close to 5500 Kelvin. This is necessary to make them compatible with the majority of daylight balanced films that nature photographers use. Also the light generated by this type of flash unit is of a very short duration. A typical burst lasts 1/1,000 of a second or shorter. Some of the higher powered and more expensive units can burst as quickly as 1/10,000 or even faster. These quick bursts can be used very effectively to freeze movement, such as a hummingbird's wings.

Camera bodies also play a large role in using fill-flash. Cameras are designed to "synch" with the flash at a particular shutter speed. These speeds can range from 1/60 of a sec. up to a 1/250. Any shutter speed slower than this can be used but you are unable to select anything faster. If we need to use the flash in bright or sunny conditions we may have to stop the lens down a smaller aperture to accommodate the slower shutter speeds. In order to control the amount of Depth of Field and depending on the subject matter, a smaller aperture may not be a viable alternative. We need to figure out ways to overcome these shortcomings. One alternative is to chose a camera body such as Canon's EOS 3 which when used with a Canon EX series Speedlight you are able to synch your flash at any shutter speed. Another is to chose a slower speed film or use a neutral density or polarizing filter over the lens in order to reduce your effective aperture.

One of the drawbacks to using a flash in the field is the output strength of the unit itself. The light has a tendency to fall off very quickly and is unable to span long distances. This is not a problem for objects that can be photographed close-up such as flowers or insects, but can be almost useless for large mammals photographed at distances of 50 - 100 feet or more. The camera's built in flash typically becomes useless at distances beyond 10 feet so a hot-shoe mounted unit becomes the necessary choice. A flash extender or Fresnel lens can also be used to increase this working distance by concentrating the light beam and focusing it in a much smaller area. These add-ons normally will increase the flash out put by two to three f/stops. This type of extender typically must be used with lenses of 300mm in length and longer. Shorter lenses will cover a larger area than the flash does and you end up with a portion of your image being spotlit.

Until recently, the main disadvantage to using fill-flash, especially on mobile subjects, was the difficulty in determining the flash exposure. Since the flash to subject distance determines the exposure, using it on anything other than stationary objects was very difficult. With todays newer TTL cameras, a lot of that exposure determination is done for us. However, if your camera and flash unit don't allow for TTL exposure, these same automatic principles apply to any flash unit that has a thyristor or some sort of built in automatic meter.

Fill flash is used whenever we want to fill in shadowed areas of our photographs or whenever we want to balance the tonal range of the image to within a range that the film can record. Lets look first at using flash in bright sunlit conditions.

We are photographing a nice mule deer buck that we have been working with from first light. Three hours later the buck has now laid down in the shade to escape the hot sun. With fill flash we can balance the light falling on the buck in the shade with the background that is lit by the bright sun.

In this type of situation I typically begin by metering the light falling on the background. I set my camera body to its fastest flash sync speed of 1/250th sec. Metering the background gave me a reading of 1/250 @ f/11 with 100-speed film. I want to open one stop from that reading in order to keep the background looking light and natural. I now have an exposure of 1/250 @ f/8. Using my TTL flash I set the exposure compensation dial to -1/3. I have found that "dialing the flash down" in this manner, helps to avoid the "overflashed" in my images. This is also a great example of how a faster synch speed can be beneficial. If my camera were to synch at 1/60, my exposure would be 1/60 @ f16, possibly providing more depth of field than I desired in this situation.

Another excellent time to reap the benefits of fill flash is when your subject is in very bright, direct overhead light. This type of light creates a lot of contrast between the highlights and the shadows. We can use our flash to add detail to those shadowed areas and more effectively balance our exposure. Since our main light source is the sun our exposure calculations become easier than our previous scenario. Setting the camera to its fastest synch speed (1/250) and using a 50-speed film our exposure is measured at 1/250 @ f/8. The only thing left to do at this point is to set the amount of "fill-in" we want from our flash. My experience has been that adjusting the flash -2/3 to -1 stops down gives the most pleasing results. You don't want the flash to be your main source of light, you just want to bring some light and detail to those heavily shadowed areas. Much more detail has been gained in the shadowed areas of the snake, opposed to the image where fill flash was not used.

Using flash in overcast light can help to bring extra sparkle to your images as well as add a little more depth. Be very careful not to overpower the softer ambient light, as all we want is to add a little spark to the image. Since overcast light can sometimes carry a blue or "cool" tone our flash unit that is daylight balanced can actually warm the image a little. You could even add a slight warming filter to the flash head to warm it up even more. Theatrical supply companies that sell lighting supplies can be a great source for flash filters. (TIP: their old sample packs can even have the exact size gels to fit your flash head and they sometimes give these away free.)

In this type of light, your shutter speed is much slower than in the bright sun and it is important to ensure that it is fast enough to stop your subject's movement. Although the flash can freeze motion, it is not used as a main light and if you are not careful you can end up with a ghost image. One exposure comes from the ambient light and can be blurred and a second more faint but sharper image can come from the lower output flash. While this can be a creative technique, ensure that this effect is what you are after.

In the image of the mallard drake, the light is low and a 1/30-sec. exposure @ f/5.6 was required. In low light such as this a direct on camera flash can also create eye shine. This is the same phenomenon as "red eye" in humans and can only be eliminated by moving the flash off of the same axis as the lens. You must use an off camera synch cord and a bracket. Or you can achieve the same results by holding the flash off to one side by hand.

I set the flash -1 1/3 below the ambient exposure using the flash compensation so as not to overpower the image. I will typically use a much lower amount of fill (more negative compensation) in overcast situations to avoid overdriving the ambient light. In this case it was just enough to add a little highlight to the water drops on his head and neck and to give him a catch-light in his eye. I also moved the flash approx. 12 inches off camera by order to avoid the possibility of eye shine. My experience has been that any image made in light measuring lower than 1/250 @ f/2.8 (or equivalent exposure) has the possibility for eye shine so I try to move the flash off the lens axis whenever possible. How far you move the flash will be determined by how close you are to you subject as well as how your subject's eyes are positioned on their head. For example, mountain lions eyes located on the front of their head will reflect differently than a deer's eyes whose eyes are located on the side.

Practice, practice, practice! Experimenting is the best way to determine which flash settings you prefer and how your particular setup reacts to each situation. Subjects both lighter and darker than neutral can also fool the cameras TTL metering system so bracket your exposures if you can to ensure the best results. If you feel somewhat overwhelmed by all of this, you are not alone. Break each of these steps down into pieces and remember the basics of exposure and light and you can quickly turn your more mundane images into real showstoppers.

All text and images are copyright Les Voorhis (except where otherwise noted).

About the Author: Les is a professional nature/wildlife photographer based in Lakewood, CO. An avid outdoorsman, Les has photographed our nation's back roads extensively with heavy concentration in the Rocky Mountain west. He often heads off the beaten path to areas rarely traveled by others. His affinity for all things wild and unspoiled has allowed him to find and capture magnificent images on film. From the wilds of Alaska to the busy roadways of Rocky Mountain National Park, he has successfully photographed some of the United States' most prolific and sometimes elusive wildlife. Elk, Mule Deer, Bald Eagles, and Mountain Goats are favorite subjects. In the silence of the predawn hours, he forms a magical unspoken bond with his subject. That magic is then transferred to film. His exceptional eye for dramatic light is apparent from his majestic mountain scenes to his delicately detailed macro work. Les offers photography seminars in the Denver area. He is actively shooting to add to his extensive stock photography file. Les' images can be seen regularly in national and regional publications including Rocky Mountain Game and Fish and Colorado Outdoors, Bugle Magazine and American Hunter. A selection of his fine art prints is currently being showcased in Colorado galleries and gift shops.

You can see more of Les's work at the following websites:
Profotos - Les Voorhis


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