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Figuring Flash To fully understand and utilize your camera and equipment, you should learn next about flash and how it operates. In most instances you will count on the natural light from the sun to provide illumination for your photographs. In other cases artificial light, such as that from indoor lamps or fluorescent fixtures, supplies the illumination, however, there are occasions when little or no light is present, and you have to provide some quickly in order to make your pictures. This is done most easily with the use of flash.
At night, off the camera, flash can be fired several times during a time exposure to light up a large subject, like a statue or the front of a building. Flash also is valuable for close-up photography, because the bright flash light lets you use small lens openings for better depth of field. Before learning more about flash techniques, you should become familiar with electronic flash equipment. Using Electronic FlashEarly electronic flash units were bulky and expensive, and they were used mostly in photographic studios. Because advances in electronics have produced smaller, more versatile, and less expensive units, shelves of camera stores are loaded with an overwhelming variety. Accessory electronic flash units are made by camera manufacturers for their specific models, as well as by photo equipment companies for use on various brands of cameras. Before purchasing any flash unit, consult the unit's instruction booklet for technical data and take the following information into consideration. The two major types of electronic flash are manual and automatic. With a manual electronic flash unit you determine the exposure by setting the cameras lens opening. First you figure the distance between the flash and your main subject and then you refer to a chart on the flash unit that indicates the correct f/stop to use, according to the ISO speed set on the camera. For very accurate flash exposures, a TTL dedicated autoflash is the choice, which means that the flash unit activates through the-lens flash metering at the inside the camera instead of relying on the unit's internal sensor to determine exposure. That feature also allows you a wide choice of f/stops for better control of depth of field; with non TTL units you may be limited to one For proper exposures with any autoflash, whether an accessory type or built into the camera, the most important thing for you to know is the flash's minimum-maximum automatic operating range. That tells you how close and how far away your subjects can be in order for the autoflash to make correct exposures. Some units have a rather limited range, like 4 to 12 feet, while others offer more extensive coverage, such as 2 to 40 feet. As you’ll discover, if a subject is closer than the flash’s minimum distance, the picture will be overexposed; if it’s farther than me maximum distance, an underexposed picture will be the result The unit's technical data will indicate the automatic operating range in feet (or meters). With units that permit a choice of f/stops for better control of depth of field, the autoflash operating range will change according to the lens opening you choose. Another important consideration in choosing an electronic flash unit is the width of its coverage, often called the angle of illumination. The flash should cover the angle of view of the lens you are using in order to provide uniform lighting. The angle of illumination may vary according to whether the flash unit is held horizontally or vertically (see the flash unit's instructions). Some units are designed especially for use with wide-angle lenses; others will accept a wide-angle attachment to spread the light. A few units feature a 200m head, which can be adjusted for use with either wide angle, normal, or telephoto lenses so the flash will provide the proper angle of illumination. Regarding the more common source for power, batteries, check in the Hash unit's instructions for two significant factors: the recycle time and the number of flashes before the batteries must be replaced or recharged. A short recycling time means you won't miss the action, or bore your subjects, while waiting for the unit to be ready to fire again. (The batteries must charge an electrical capacitor that provides the energy to create the bright burst of light.) Recycle times can range from one-half second to 15 seconds; the fresher the batteries, the faster the recycle time. Likewise, the greater the number of flashes, as indicated in the unit's technical data, the longer you can use the flash before installing new alkaline batteries or recharging ni-cad batteries. lf you use flash only occasionally, rechargeable ni-cads may be the most economical because alkaline batteries also lose their charge over time and must be replaced whether or not you fire the flash. Some autoflash units feature power-saving circuitry that provides faster recycling times and more flashes per recharge or new set of batteries. Such circuitry prevents the capacitor from losing all its electrical charge after the unit's sensor or "ITL metering system cuts off the flash when sufficient light has been provided for an exposure. All electronic flash units feature a ready light or audible signal to indicate when the capacitor is charged and ready for the flash to be fired. lf you take a picture before the ready light comes on, the flash may go off but it probably won't have sufficient power to make a correct exposure. Cautious photographers even wait few seconds after the ready light glows to be sure the capacitor is fully charged. Most of the better autoflash units have a sufficient light indicator that lights or makes a sound to signal whether or not the Hash light was adequate for a proper exposure. lf it warns you that the light was insufficient, get closer to your subject or use a wider lens opening. To check exposure without taking a picture, press the unit's open flash button to see if the sufficient light indicator signals that the autoflash output is adequate. The most versatile units have a tilting and/or twisting flash head, which can be adjusted for bounce light and still allow automatic operation when mounted on the camera. Some feature TTL metering or have an accessory or detachable sensor that remains on the camera to provide autoflash exposures when the unit is removed from the camera position or aimed for bounce light. Flash Contacts and CordsUnless electronic flash is built-in, 35mm cameras usually have a mount on top of the camera to hold a flash unit. Called a hot shoe, it’s electrically wired and makes contact to the flash when the unit is inserted and locked into the shoe. Because the flash is triggered through the hot shoe contacts when you press the camera's shutter release, the hot shoe eliminates the need for a flash connecting cord, which can come loose, break, or get in your way. With dedicated autoflash units, the hot shoe also transmits the flash’s signals to the viewfinder to indicate when the unit is ready to fire and if the flash light has been sufficient for a proper exposure. A drawback of any hot shoe is that it holds your flash in one position on the camera and does not permit variation in lighting, Some units partially overcome this problem with a tilting and/or twisting head, which can be adjusted to change the direction of the flash, most often for bounce lighting. For complete control you need a flash connecting cord. With it the Most cameras have a small socket, sometimes marked with an X, where a flash cord can be connected. Other models require that a socket adapter or special flash cord be slipped in the hot shoe, especially if you want to utilize the features of an autoflash or dedicated unit when it’s taken off the camera. Flash cords come in various lengths, either straight or coiled. When buying one, take your equipment to the camera store to make certain the cord's plug fits your cameras flash socket and the flash unit. Flash cord sockets on cameras commonly take a PC (push contact) pin-type plug. Always check that the plug is firmly inserted in the socket so the flash will fire. lf the plug is loose, its rounded tip can be squeezed carefully to make it fit better. When frequently unwound and rewound, or twisted, flash cords can become damaged or broken. lf your flash unit fails to work, its connecting cord may have been severed internally. To test for a faulty cord without taking a picture, disconnect and short-circuit the flash cord plug with a paper clip or pin. The unit should flash. lf not, wiggle the cord while short-circuiting the plug. If it flashes then, the wires in the cord are probably broken and make contact only occasionally. Get a new cord. Also be aware that the most common reason a flash does not fire, whether attached by a flash cord or mounted in a hot shoe, is because of poor electrical contact at the battery terminals. An almost invisible corrosive film can develop and
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The short burst of flash light also means you’ll avoid blurred pictures caused by inadvertent camera movement. And you can bounce flash off a ceiling or wall to improve interior shots being exposed by natural light. Besides its uses for indoor photography, flash is a big help outdoors in daytime to fill in any shadows on your subjects, especially their faces. The extra light will give detail to facial features and add a sparkle to the informal portraits you shoot in daylight on dull days flash can be fired to brighten up nearby subjects. In some back lighted situations, such as photographing people in front of a sunset, flash will illuminate your foreground subjects so they won’t be silhouettes.