Quick Guide to Understanding Aperture

Aperture Information

In the dictionary the term Aperture has this definition: "a usually adjustable opening in an optical instrument, such as a camera or telescope, that limits the amount of light passing through a lens...."

All lenses have an opening (Aperture) that allow light to pass through to the camera's image sensor (digital) or film. A larger aperture, (measured in fractions: i.e. f/3.5) allows more light to pass through while a smaller aperture (F/22) allows less light to pass through. The size of the aperture, or its range is determined by the lens itself. If you look around the front of the lens on your camera you might see "f-stop" numbers listed. An example may be: F3.8 - 5.4. These number tell you how large the opening of the lens can get at wide angle (F3.8) and at the telephoto setting (F5.4). In this example "zooming in" will allow less light to pass through compared to shooting the same scene at wide angle.

The smaller the F-stop (fraction) the larger the aperture (opening) of the lens can be. An F-stop of F2.0 lets in more light than a setting of F2.8, etc.. A lens with a maximum F-Stop of F2.8, F2.0, or F1.8 are considered fast. Most consumer priced cameras usually offer a maximum opening size of F3.5 or F3.8 which are fine for normal everyday shooting but not great when trying to reduce motion blur in lower light situations (school plays, indoor sports).

A larger lens opening (brighter lens) offers the following advantages:

• You'll be able to shoot more often with just natural lighting. This helps to reduce harsh shadows and red-eye caused by flash. A flash will still be needed when the scene is too dark, even for the bright lens.
  
  
• By allowing more light to pass through, the camera will be able to choose a slightly higher shutter speed which helps to reduce motion blur when shooting in less than ideal lighting conditions.
  
  
• A larger aperture (F/5.6 in photo example) helps to reduce "depth-of-field" (the amount of area from front to back that stays in focus) which makes for beautiful portraits (sharp subject, blurred background).