Lightning results when charges are separated in a cloud, and induce a charge on the ground. When the charges are large enough, the electrons travel from the negative region to the positive charges in a discharge. Discharges can be between the cloud and the ground, or between the cloud and another portion of the cloud. When a discharge occurs, an enormous number of electrons move, and literally rip other electrons from their molecules as the lightning passes through the atmosphere. The recapture of electrons by the charged molecules gives off light.
Since the cloud sends many electrons through the air at one time, they overwhelm the area they strike, giving that area has an excess of negative charges. Many return via the original charged air column where some charged molecules have yet to capture electrons. This process repeats, with a flickering of lightning that lasts for some time.
Photographing lightning requires overcoming several obstacles. Although lightning may last for some time, it is not a long enough duration to allow a photographer to focus a camera and to open the aperture. One must have the camera set for distant objects, and have it aimed in advance. But that is difficult, since we never know where the next lightning bolt will be. So, it becomes a process of set, aim, and hope.
Even if the camera happens to be properly aimed, the reaction time in opening the aperture is determined by reaction of the photographer, and is usually to long to capture the image.
Leaving the aperture open using a time exposure requires the surroundings be dark, or light from the surroundings will flood the image, rendering it unusable. Setting up with a street light to the side is not acceptable for night time exposures. The incidental light will flood a time exposure photographic attempt. A second problem is the brilliance of the lightning. If the aperture is open too long the image may itself flood too much light into the camera. This is more of a problem with digital cameras, since slow film designed for such events cannot be used in them. Yet many people have now gone to digital. Too fast of a camera speed may catch the flickering lightning at the instance it is dark, missing the opportunity. This is also a problem.
Still another concern is safety. Lightning must be photographed from in front of the storm, since photographing through rain is impractical. But lightning may strike ahead of the storm, and frequently does. Keeping the photographer safe is a necessity. But photographing from indoors has a drawback. The brilliance of the flash of lightning often illuminates the interior of a room, and that light reflects off of everything within the room illuminating the glass window from the inside. This causes the same problem as using a flash to tale a picture at night through a window, the image of everything inside the room reflects from the window into the lens and is caught in the photograph as an aberration looming.
This article is provided by Henry M. Smith of Black Spaniel Gallery. Please visit us at blackspanielgallery.8m.com