Photography Basics: All About Aperture

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Aperture and other technical photography basics can induce yawns in the most eager of budding shutterbugs, but once these basics are understood, the rest of photography easily comes into focus. Aperture, ISO and shutter speed are all important terms to know, whether you have a point-and-shoot or a professional camera. This article explains aperture and provides tips for using it to create better photographs.

To best understand aperture, consider how the irises of your eyes widen and narrow to allow more or less light into the pupil. Like your irises, the camera's lens diaphragm narrows and widens to let in less or more light. Thus, the aperture dictates the exposure (the darkness or brightness) of the photo. The aperture also has another important function which we'll look at shortly.

"Aperture" refers to the size of this opening and is measured in F stops. The smaller the F Stop number, the wider the aperture. This is where it's easy to get confused. Actually the F stop numbers are ratios, which is why the bigger the F Stop number, the smaller the size of the aperture.

In addition to controlling light, aperture also controls depth of field. To better understand this, make a fist and hold it in front of your eye. Now slowly open your hand. See how the focus changes? Sure you can see more through the bigger opening, but when the opening in your fist is small everything is in focus? Try it again, and notice how when you open your fist, the object closest to you will come into sharp focus while objects farther away will be out of focus. This is how aperture determines depth of field, that is how much of a photograph is focused.

If you are taking pictures in Auto Focus (AF), the camera will attempt to focus on what it sees as the main subject, but often it may not be what you want.

For this reason, many cameras have an Aperture Priority setting. This allows you to set the aperture and then it automatically adjusts the shutter speed to compensate for the aperture. For example, if you set the aperture for a landscape, this narrows it, thus letting in less light. The camera would then automatically increase the amount of time the shutter stays open so that your photo isn't underexposed or too dark. Aperture Priority isn't perfect, but generally this how it works.

Now if you have an SLR and are taking pictures in manual mode, you can adjust the shutter speeds and aperture separately.

Most will have a camera with preset modes, such as portrait, landscape, sports, etc.
When the mode is set for landscape, the aperture automatically narrows so everything will be brought into focus. At the same time, the shutter speed automatically slows down, leaving the shutter open longer to offset the smaller amount of light coming through the lens diaphragm.

When you switch to portrait mode and focus on someone in front of you with the landscape in the background, the camera will make your subject in focus and make them stand out from the background. And it will speed up the shutter speed so the picture isn't overexposed by the additional light allowed in with the larger aperture.

Remember: the smaller the aperture, the greater the F stop number (because it represents a ratio not a whole number) and the greater the depth of field.

Understanding photography basics like aperture is not only important for those using manual settings or Aperture Priority, it also helps those using preset modes. Here are three preset modes you should better understand:

  1. Portrait: How much the background blurs when using this mode depends on your camera and the distance between your subject and background - a minimum of 10 feet works best. This mode can be used for any subject you want to bring into focus while taking the background out of focus.
  2. Landscape:(called "Infinity" on some cameras): This is the mode depicted by the mountain peak or figure 8. You can use this for anything where you want everything in the picture to be in focus, such as seascapes, cityscapes or your garden.
  3. Macro: This mode, depicted by the tulip, opens  the camera's aperture extra wide so that you can take extreme closeups without the blur caused by not enough focus. Depending on your camera, you'll be able to get anywhere within an inch to a foot of your subject. When preparing to take pictures outdoors of things like flowers, keep in mind that due to the slower shutter speed, even the tiniest movement of a petal can cause blur. Also remember to focus on the subject that you want in focus, whether it be a caterpillar's eyes or a butterfly's wings.


Just applying this knowledge can help you produce some beautiful photographs that you'll be proud to frame on your wall.

Autumn Lockwood loves taking pictures and is a writer for Your Picture Frames. Your Picture Frames offers an enormous selection of picture frames in all sizes, shapes and colors. Shop online and see our selection of big wood and metal frames and small sized photo frames. Visit our website or call us at 1-800-780-0699.

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