Basics of flash:
Flash photography is known to many as that annoying flashing bulb that goes off with each picture. Flash photography goes to a much more advanced level. On a dSLR, most of the consumer cameras have a built-in pop up flash. This flash is usually a little bit better than those provided on a point and shoot camera. Where flash photography really shines is when an external flash unit is provided. These are more powerful and offer a higher level of control. They also allow the ability to use light modifiers to change the way the light behaves. There are two main types of flashes. The first is the speedlight. It is a flash gun that can be mounted onto the hot shoe of a dSLR. Nikon and Canon both provide systems where multiple flash guns can be used in single picture, all synched and controlled wirelessly. The second type are studio strobes. These are large units requiring stands and an ample power source. They provide an even more powerful flash and can mount larger modifiers appropriate for use on groups of people.
The speedlight:
A necessity in flash photography that vastly outperforms the onboard flash. Modern dSLRs can control the flash output via TTL (Through The Lens) metering. This gives a good exposure and without a lot of guess work.
Usage:
After learning the basics of exposure and being able to shoot good photos with available light, adding a speedlight to the equation increases the complexity of the shot while also opening up more options.
Fill flash is a photo enhancing technique that adds light to some shadows which otherwise would be a well lit scene. The most prominent example is shooting people outside. By some strange phenomenon, a person is almost always darker than the scene. You set the camera to expose correctly for the scene. Your subject will be underexposed and the flash is used to fill in the shadows. The result is a well balanced exposure. This is especially true for backlit situations where the light source is behind the subject.
Here is an example of a fill flash shot. The couple is underexposed when shooting with only available light, so flash was added to bring them out of the shadows.
The second and more prominently known use is acting as a main source of light in a dark situation. A straight on firing with the flash usually produces less than desirable shots. They usually end up being very flat and seemingly overexposed. However, with practice and creativity, a direct flash can produce good quality.
Direct flash:
Using a light modifier such as a soft box will soften and diffuse the light, resulting in softer shadows. The goal a softbox is a box made of fabric that goes in front of the flash and has a diffuser panel. The goal is to make the light source bigger. The bigger the light source is relative to a subject, the better the quality of the light.
Direct flash with a mini softbox
Another technique that makes the light source very large is bouncing. This works well indoors and the room has light colored walls. Most flash guns have the ability to turn the flash head itself. So this technique is accomplished by pointing the flash straight up at the ceiling, or one of the ceiling edges opposite from the subject. This requires a large amount of power from the flash unit.
Bounce flash off ceiling
Modifiers:
Softboxes have been mentioned earlier. They range in sizes from a small rectangle to huge boxes that are the size of two people or larger. They can be mounted on flash guns or more commonly, studio strobes. The produce a diffused, directional light that can be easily controlled. The downside is that they are large and cumbersome, usually only practical in a studio or with many assistants.
Umbrellas are another modifier available that will be discussed with the studio strobes.
Diffusion domes are a little plastic box that slips over the head of a flash gun. It helps diffuse the light even more when bouncing flash. The Stofen Omnibounce is a very popular diffusion dome. Nikon provides a similar dome with their SB-800 Speedlights.
Another common modifier is the Gary Fong Lightsphere. It is a half cylinder contraption that mounts on the flash gun and bounces light straight to the subject. More information can be found at his website.
Flash brackets attach to the camera and flash gun to move the flash unit off the camera and further away from the lens. They also allow the flash unit to remain in the same position relative to the lens whenever the camera is in a horizontal or vertical position. The result is no more red eye, more contrasty image, better direct flash results, and it hides shadows behind the subject.
So that is the very basics on camera flash units. Next up: studio strobes.
