Photographic Exposure 

Good photography is all about capturing light on your terms. By first learning some of the basics about how your camera works, you'll soon develop your techniques and learn to deliver your photos artistically, drawing your audience into a moment or a scene instead of just showing them a picture. When it comes to taking control of your pictures, there are a few key things to know about.

Exposure
Whether it's automatically adjusting your settings or just providing light read-outs based on your manual settings, your camera clearly has a goal for your pictures. That goal is to expose the film or image sensor to an exact amount of light to produce the clearest image possible.

An overexposed shot will lose detail to a bright, washed out look, while an underexposed shot will lose detail to dark areas where insufficient light was collected. In order to get a perfect exposure, your camera needs to know what color the scene is so it can determine how much light is needed. How does it tell what color your subject is? It doesn't; almost all cameras assume the subject is gray, which as it turns out, is pretty accurate.

In most cases, if you were to mix all the colors of a picture together you would produce a grayish color - or more specifically a certain shade of gray known as 13% gray.

When set to automatic focus, your camera will adjust its shutter speed, aperture setting, and ISO speed to produce the most detailed picture, assuming the subject is 13% gray.

You can do a lot of interesting things by manually adjusting these settings, but bear in mind you'll need to keep them all balanced properly to avoid over or under exposing your shot. By using a hand held light meter you will significantly improve your pictures.

Aperture
The aperture refers to the opening that admits light into your camera lens. The size of the aperture is controlled by a diaphragm, a device consisting of several overlapping blades of some opaque material which by sliding in unison toward either the perimeter or center of the camera lens cause the aperture to dilate or constrict. Aperture settings on your camera are measured in f-stops, with the lower numbers describing a larger or more dilated aperture, and larger numbers describing a smaller aperture.

The size of the aperture controls the depth of field on the resulting photograph, meaning basically how much of the image is in focus. With a high f-stop setting, (that's a constricted aperture), you can obtain a photo that is crisp and detailed throughout the field of view. With a low f-stop setting, the resulting photo will only be detailed around the focal point of the shot, and will be blurred elsewhere. This effect can be very powerful in directing your audience's attention to a specific portion of your photograph.

It's important to remember that low f-stop settings allow more light through the camera lens, and could easily overexpose your shot if you don't compensate with shutter speed or ISO speed.

Shutter speed
The shutter speed determines how long your camera's image sensor is exposed to light. Depending on your camera, shutter speeds range from a full second on the slow side, to about 1/1000 of a second on the fast side. A shutter speed of about 1/125 of a second would be considered pretty normal for a photo in daylight settings with no fast moving objects.

Shutter speed, or exposure time, plays a huge role in determining how detailed your photograph will turn out, and how evident any motion in your shot is. Fast shutter speeds are used for creating crisp, clean shots of well lit, and even moving, objects. Sports photographers, for instance, might use a fast shutter speed to capture an action shot in daylight settings without losing any detail to blur. Slow shutter speeds, on the other hand, can be used to take pictures of still objects in low light, or to create a varying amount of motion blur.

If you're trying to take a picture in low light, remember that keeping the subject and your camera still and stable during the exposure is the key to a clear picture. Try using a tripod and setting your camera's timer so you're not touching it when the shutter is open. Much like the other settings on your camera, make sure to compensate for you shutter speed with aperture and ISO settings so that you get the right exposure.

ISO speed
The ISO setting on your camera determines how sensitive the image sensor is to light. In case you're wondering, ISO stands for the International Organization for Standardization, and is simply a standard in light sensitivity applied to video devices. A higher ISO setting will cause your camera to become more sensitive to light.

High ISO settings can be useful in extremely low light conditions, when a dilated aperture and slow shutter speed are insufficient for properly exposing the photograph. Inversely, low ISO settings can be useful in very bright conditions when your aperture and shutter speed settings cannot capture the level of detail you're after. It's worth noting that very high ISO settings tend to introduce grain or noise into the darker areas of your image.

Basic knowledge of your camera's aperture, shutter speed, and ISO settings is a great foundation to start building your own techniques on. With a little time and a lot of experimenting, you're sure to discover a variety of ways to create captivating, powerful photographs.