Pixiq

Join me on Facebook. Become a 'fan' of my Facebook page on Experimental Digital Photography. Click on the 'like' button at the top of the Facebook page.

Flash is the most controllable light source available to photographers. When the available light is dim or doesn’t exist, a flash can be quite effective for filling out an exposure. Night and low light photography in particular benefit from using flash, if you know what you are doing.

Light Falloff: The Inverse Square Law

The inverse square law states that the strength or intensity of light is inversely proportional to the square of the distance from the light source. In more common terms, an object that is twice the distance from a light source will receive a quarter of the light’s intensity. A subject lit by a flash from 10 feet (3 meters) receives a quarter of the light that the subject would receive at 5 ft (1.5 m) from the flash.

You can use this physical characteristic for artistic purposes. For example, if you want a portrait of a person to be against a primarily black background, simply place the person a good distance away from any background. The light doesn’t reach the background, thus making it black or a very dark. If you want to illuminate the background, set the subject closer to it. The images on the next page illustrate how the background drops out—and how it quickly drops off—when using flash at night.

In-Camera vs. Accessory Flash Units

While we could devote an entire book to flash, perhaps this brief introduction will help. There are essentially three kinds of flashes:

• The built-in/in-camera flash

• A dedicated flash that is designed to work with your particular camera but which must be bought separately

• A third party flash made by an independent company

Each flash unit has its strengths and weaknesses. The built-in flash unit cannot be moved since it is part of the camera. It typically creates very flat, one-dimensional lighting. In addition these flashes are not very powerful yet can drain the batteries in a camera quickly. However, the built-in flash is already paid for, works with a camera’s features, and is easy to use.

A proprietary dedicated flash—made by your camera company for your camera—is often the best bet for people who want a more powerful unit. This unit can be controlled directly from your camera. It can be used on or off the camera, and can create a much more dimensional light than the built-in unit. It uses its own batteries so the ones in the camera are not drained.

A third party flash may have additional features not found in either the built-in or dedicated flash unit, but because it was not designed for your particular camera, might require a learning curve in order to use it adeptly. Third party flashes may not work with all of your camera’s features or programmed functions, however, many manufacturers (such as Sunpak) design units to work with the more popular cameras.

Adjusting the Flash Intensity

Many high-end cameras allow you to adjust the intensity of the flash, especially if you use an accessory flash unit. Using a higher ISO will also allow you to lower the flash power. And remember, the lower the power, the longer your batteries will last, as even new flashes tend to eat batteries.

Getting Ready for a Shoot

If you plan on taking a number of photos at an event, work out the kinks of your flash setting by taking a number of test shots before the activities start. You don’t want miss great opportunities because you are not prepared. Remember to pack plenty of batteries; flash uses a significant amount of battery power

Slow Sync Flash

The slow sync flash setting allows you to mix flash and ambient light when shooting at slow shutter speeds. The burst of light emitted from a flash unit is very fast, as fast as 1/1000 second even for an in-camera or low-end accessory unit. Because flash is so fast, the camera’s shutter speed often does not determine the sharpness of the image; instead, the flash’s speed determines image sharpness. Also, because the flash burst is so fast, the image should be very crisp. This means that experimental photographers can combine a subject’s face lit with flash, for example, with the sweeping blur of traffic lights at night into one exposure. This is accomplished by using the slow sync flash feature to create a long exposure that captures the ambient light, such as traffic lights in the background, and the flash burst to expose the subject.

To create a well-balanced slow sync image, you will need to make two decisions: how you want to expose for the ambient light, and how the flash will light the scene. The first decision deals with a number of things, including evaluating the general environment and determining the overall exposure for the image. Take a number of test shots to find the appropriate shutter speed and f/stop for your surroundings; for experimental photography the shutter speed might be several seconds or more.

The second decision you must make involves the flash. Take some test shots with the flash at the normal flash shutter speed (usually about 1/125 second) along with the f/stop you determined for the surroundings in the first exposure. Think about how you want to adjust the intensity of the flash. Also be aware that the distance between the flash and the subject is important; remember light intensity diminishes at the square of the distance. (For example, if you are including a person as your flash subject in the picture and the person is too dark even at the highest intensity, move that person closer to the camera or move the camera closer to the person.) Keep the background of the composition in mind; any object close to the subject will pick up more light from the flash, and objects at a distance will reflect a significantly less amount.

Once you have made these decisions, combine them in this manner: set the camera shutter speed and f/stop for the exposure you determined for the ambient light and set the flash intensity to the level you choose. Lastly, choose when you want the flash to fire—at the beginning or at the end of the exposure.

 Note: Front or Rear Curtain Sync

 In high-end cameras, slow sync flash often comes in two modes. You can adjust the setting so that the flash goes off at the beginning (front curtain) or at the end (rear curtain) of the exposure.

Hands On:

Slow Sync Flash

•    Take a friend outdoors at night where there is traffic or moving lights in the background. Avoid places where the person’s face is close to other objects like a tree or lamppost as the flash will illuminate these as well.

•    Set the flash to slow sync and decide if you want the flash to go off at the beginning or at the end of the exposure and make the necessary setting changes.

•    Next take a 4 to 8 second exposure of the friend; you do not necessarily need a tripod in this case. However, do it both with and without a tripod if you want to see the difference.

•    Adjust the flash so that it illuminates only the person’s face and not much of the surroundings.

Some variations:

Handhold the camera with the flash set to go off at the beginning; move the camera around before or after the flash fires. This “paints” the lights into the background while the shot of the person is still sharp. (See Chapter 6 for more about painting with light.)