Photography by definition is a "light picture". As we all know it is the quality of the light falling on our subject that can make or break the image. Unless you have a special power over the sun and clouds, we as nature photographers have no control over the light in our scenes. Or do we? Utilizing a portable electronic flash we, all have the ability to control the light and contrast in our images, even in large-scale landscape images.
For years electronic flash was a tool of the studio photographer. Size, portability and the difficulty in establishing flash-to-subject distances made field flash difficult, if not impossible. The advent of Through-The-Lens (TTL) technology and digital cameras is not only making flash easier to use but also a very powerful imaging tool. We can now extend our shooting time further into the day, fill in shadows as well as add punch to drab scenes in overcast light.
Many people argue that using fill flash makes images appear unnatural and "over flashed" and should be avoided. While this is possible, balancing the flash correctly with the existing ambient light is key to making the image appear as if no additional light has been used. This can be accomplished by dialing the output strength of the flash up and down to create the desired effect. The key here, I have found, is that the stronger the ambient light, the stronger the necessary output of your flash and vice versa. Tonality of your subject comes into play as well, and we'll cover that in a minute.
During the course of this article we will be discussing using flash only as a complement to existing ambient light and not as a main light in itself. Settings for a main light can be quite different, and some of the rules don't apply. I have found that keeping the strength of your flash between -2/3 of a stop to -2 stops below the ambient light seems to work the best. That is over 1 1/3 stop difference, so how do you know when to use what setting? First, I take the strength of the ambient light into consideration. If filling in shadows created by a strong direct sun or by filling in the shadowed side of a backlit subject I will typically set my flash stronger than if the light is softer and more overcast. The next topic of importance is the reflective qualities of your subject. Is your subject white or light colored or is it black? Maybe it is somewhere in between? The general rule of thumb here is that the brighter the subject the less fill that is necessary. In contrast, the darker the subject, the more it will tend to soak up light, so it will require a much stronger fill.
Lets look at a few examples that may explain this more effectively. We'll start with a medium toned subject in soft overcast light. This seems to be the situation where I use fill flash most often. In the image of the house finch on the snowy evergreen tree, I set the flash to fill in the bird at -1 1/3 stops below the ambient exposure. The lower setting on the flash helps to keep the overall soft look to the image. Were this image made in stronger light, I would have set the flash higher, closer to -1 or -2/3. The stronger the ambient light, the less risk there is of making the image look "over flashed". The warmer color temperature of the flash compared to the cooler overcast light helps to warm the image and make it more appealing to our eyes as well.
Next, lets look at an image made in more direct light. The flash output will be set higher here than in the previous image due to the stronger ambient light. The golden-mantled ground squirrel image was made at an impromptu feeder setup during the middle of the day. Images such as this are one of the advantages of using fill flash, as it greatly extends our shooting time. With direct overhead sunlight, I set the flash at -1 to help fill in the area directly below his chin and on the shadowed side of his body. I also have images from this series made at -2/3 and they work very nicely as well. In order to take advantage of greater reach and faster recycle time for the flash, I also attached a Better Beamer flash extender. I will often use a flash extender to increase my flash's range and recycle time and in general the settings I use remain the same as when using a flash without an extender.
Next, let's look at an image of a subject lighter than neutral. This snowy owl image was made on a very overcast day when the light level was very low. Due to the low light and the high reflective value of the subject, I dialed my flash down to -2 to again avoid detection of the flash. A quick note here regarding using a flash on animals in low light... In order to avoid the light from the flash reflecting off the back of the animals eye and imparting a strange glow, hold your flash off of the lens axis of the camera, either by hand or by using a flash arm. In this case I held the flash about 24 inches off to the side of the camera by hand as owls have a huge pupil and seem to produce "steel eye" even in bright light.
Animal portraits are not the only nature subjects where flash can be helpful. I have begun using it more and more with landscapes to help bring attention and color to certain parts of the scene. This is particularly useful in softer, overcast light but can work in stronger light as well. The yellow cone flowers in front of the Maroon Bells were brightened significantly by setting my flash at -1 1/3 and holding it low and off to the side of the camera. This can be a very useful technique not utilized by very many people and can really bring your landscape images to life.
Today's flashes and cameras do a very good job of working together to give a pleasing look to your flashed images. Depending on your particular setup and shooting style, you may find that your ideal settings vary from mine. It is important to experiment to find what you prefer and how your camera and flash communicate with each other. The number of photographers that I meet in the field who do not carry their flash surprises me. Despite the advent of TTL flash and digital imaging, I am even more surprised by the number of photographers who are still intimidated by it. So attach your flash to your camera and grab a handful of batteries and use it for something other than your daughter's birthday party.
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