According to Wikipedia, photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film. In another part of the article, it also affirms that the word photography derives from the Greek φωτός (phōtos), genitive of φῶς (phōs), “light” and γραφή (graphé) “representation by means of lines” or “drawing”, together meaning “drawing with light”. Even long before the first camera was invented, Leonardo da Vinci inscribed two clear descriptions of the camera obscura in his notebooks. On explanations of it’s principle, Da Vinci clarified that a camera obscura was merely a dark box with a very small hole in one wall t0 allow the light to come through.
You can see that photography is all about light. Light is the agent that stimulates sight and makes things visible. Light is what you need to create a low key image—or even in Chiaroscuro technique. To capture those vivid colors that your eyes see, light is required. To capture shapes, textures, colors, shades, shadows and lights, light is required. Too much light, your photos will be colorless and washed out. Not enough light, you will have nothing but blurry photos with muddy colors. In short, light is the foundation of photography. Light is everything you see in this photographic life.
Since light can completely transform your photographs, understanding your lighting conditions well and knowing how to control, how to alter your light are the first stage you need to overcome. The directions of light in photography are also important; different angles of light will render different shadows, modifying the moods and textures of your subject. A weak, diffused light will soften shadows and diminish the vibrance of colors whereas a strong, hard light will generate harsh shadows and wash out color details. While light is important for color photography, it is even more important for black and white photography. Because the color in black and white photography is substituted with the contrast between light and shadow, strong and direct light source is often the choice.
As a street photographer, I have to force myself to grow fond of any type of light that available for me work with. I don’t have the luxury of choosing the correct light source; beside, to reshoot is out of the question. To shoot with available (ambient) light, I need to memorize the color temperature chart, learn to read the shadow, know how to calculate the lighting ratio, as well as to convert color into tonality. Lot of readings and experiments.
By the way, if you’re interested in reading about natural light, Cambridge in Colour has an ingenious article on Making the Most of Natural Light in Photography. Photoinf.com also has a detailed article on Basic Lighting Techniques.
Natural light—day light or sun light— seems to be the simplest, boring type of light source to use, but in reality, natural light is the most sophisticated light source. Think about it. The color temperature is constantly changes from morning to evening. Cloudy and overcast weathers render the light different than on sunny days. Sun light on the beach is not the same with sun light in the park. Shooting on snowy ground is also not the same as shooting on asphalt surface. If you know your light well, natural light will obey your commands and be the best light source that no lighting equipment can imitate.
There are photographers who avoid to shoot with existing lights; however, I find numerous advantages in existing light photography. Existing lights grant skillful photographers opportunities to make dramatic, creative images. Existing lights also permit photographers a greater freedom of movement. The downsides with existing light photography is that it requires lenses with large aperture, some scenarios even call for a combination of high ISO and slow shutter speed. High ISO wouldn’t cause any problem with the new camera technology, but slow shutter speed is always an issue for many photographers. Don’t let your shaky hands stop you from making the shots you want. Think of it as an advantage to create some artistic blurred images.
On camera flash is the most favorable light source for consumers and enthusiastic photographers. Whereas, strobists, some reporters, studio photographers and wedding photographers are faithful devotees of portable strobes and off camera flash systems. These studio/portable strobes and ETTL flash units may seem intimidating at first, but it won’t take long for you to master the technique—studio or outdoor. David Hobby has a well-informed blog on strobist for those who would like to learn to control and modify this lighting techniques.
Clearly, the ETTL flash units are among the leading photographic light source that most photographers would rely on. Their compact size, light in weight and versatility instantly attract wedding photographers and others. These days, companies like Canon, Nikon and Olympus are continuing to improve their sophisticated ETTL flash units to fulfill our photographic creativity; however, flashguns are still rarely used in street photography—unless you’re Bruce Gilden wanna be.