Last week we touched on the concept of "exposure" - controlling the amount of light that makes it to your cameras sensor while recording your photograph. This week we'll discuss the first of three elements in what's referred to as the "exposure triangle" - Aperture.
Inside your camera lens, there are a series of blades that can be opened wide to allow in a lot of light or closed down to reduce the amount of light. The size of this opening is referred to as "f-stops". You've likely seen numbers such as f/3.5, f/8, f/22, etc. These numbers indicate how wide or narrow the aperture was set when taking the picture. While not getting into the mathematics, one thing that is often confusing when first starting out is the fact that f-stops are expressed as an inverse. That is to say, the smaller numbers refer to WIDER openings while the larger numbers refer to smaller openings and therefore, less light.
In addition to controlling how much light is allowed to pass into your camera, aperture is responsible for something called "Depth of Field" (or DOF). Depth of field determines how much or how little of your photo appears in focus. With smaller apertures (wider openings), you can make parts of your image appear in focus while the rest of the picture appears blurry (see "Barbed Beauty" image above). With higher apertures, more or all of the image appears in focus. Being able to manipulate your aperture settings gives you creative control over your photographs that just isn't possible until you venture away from using the pre-programmed "scene modes". For those of you with point-and-shoot or camera phones, this is the one area over which you have little control. You can, however, learn to use computer software to create similar depth of field effects.
That's all for this week. Next week we'll explore the second element of the triangle - Shutter Speed. Until then, take some time to learn about "Aperture Priority" with your camera and how to manipulate the aperture while shooting. If you'd like additional information on aperture, here's a link to an article over at Digital Photography School (an excellent online resource) which provides additional information.
Until next time, keep click'n.