Camera Flashes: An Introduction
Flash photography is not just for indoors or nighttime, and it can be very useful in wildlife and nature photography. One of the great inventions of modern photography is the ability to use your flash set at TTL, meaning your camera's meter will get the exposure reading through the lens and will adjust the flashes output on its own. Knowing how to use your equipment will enable you to have more flexibility and control over the end results. Having another tool to help control the light is a wonderful option.
Flash units are another tool for you to use, but learn how to use it properly by reading the owner's manual and becoming comfortable with the controls on your flash. Modern cameras and flashes are incredible at determining correct exposures and seem to know when to add fill flash and when to give a full burst of light, but I still recommend learning how to override your camera's or flash unit's programmed settings. You need to be able to control your flash just like any other part of your equipment. Many people turn on their flash and hope for the best. You can do better than that.
Like your camera, a good flash unit allows you to fine-tune the flash output and under- or overexpose the flash for a desired effect. This is especially handy when using flash in daytime uses as a fill flash to bring out details. By adding just a little light you will be able to illuminate the foreground and put detail in backlit subjects. Fill flash lets you bring out details in the shadows. Even with your subject in good light, you can use flash to put a catch light in the eye of your subject and give your photos more life. The trick is knowing how much flash is enough or too much, and this becomes personal taste. Practicing with your flash is a good way to discover what is enough for you. By under exposing the image you can add just a hint of light when a shadow covers part of the subject, while not having it appear as an artificial light source.
For some applications you need not only your flash at full strength but also a second flash to provide required light and to cover unnatural shadows. I use this technique when photographing bird's nests, where one flash illuminates the nest and one flash illuminates the area behind the nest. When doing close-up or macro-photography of small objects, you may need extra light to attain the required depth of field. As magnification increases, depth of field decreases. This means that if you are doing extreme close-up photography, you may need extra light to work at smaller apertures with a shutter speed fast enough to stop the action.
If the flash unit is mounted on top of the camera and the lens is only inches away from the subject, the flash will not illuminate what your camera is pointed at. In this case, remove the flash (or flashes) from the camera in order to put the light where it needs to be. Even in non-close-up photography, having the flash off the center of the camera will eliminate red-eye. In a pinch, you can handhold or enlist the help of someone else to hold the flash unit, and there are many flash brackets available that allow you to work unimpeded.
If macro-photography is what you really like, a ring flash or specialized macro flash may be an accessory worth using. These are flashes that fit around the end of your lens. They are much smaller than a regular flash and allow you to change the focusing distance without having to make adjustments to all the brackets. Since they are mounted on the end of the lens, they will illuminate whatever the lens is pointed at. This is especially convenient when you are working in close quarters and do not have room for a flash mounted on a bracket. It is also more compact and lighter in weight than a conventional flash mounted on a bracket. Some camera bodies come with built-in flashes that are fine in some circumstances, but they are not as powerful as a separate flash unit. There are many flash units to choose from for any camera, but in general I recommend the most powerful flash you can acquire. You may not always need the full power, but it is nice to have when the need arises. The more powerful flashes also tend to recycle faster, meaning you won't have to wait too long for the flash to recharge and be ready to use again.
Sometimes you may find yourself far enough away from the subject that your flash will not have any effect. This is a common problem when working for example in forests where the subject is living in the tops of trees. If you increase the focal length of the lens, add a teleconverter to your lens, and increase the strength of your flash, you also can add a teleextender to your flash. Just as in lighthouses where the light needs to be directed long distances to be seen, a teleextender for the flash will direct and increase the light from the flash.