Aperture in Detail

From the basics page we learned the aperture was the size of the hole the lens used to let light pass.  We also determined that the more light (lower f-stop number) the smaller our depth of field (range of picture in focus) became. Now we will get into the applications of aperture settings in basic photography.

The most obvious use of aperture settings is to change the

 field of view. Here is a clear demonstration of the depth of field.  On the left half of the image the entire half of the yardstick is in focus; the left half shot at a lower f-stop shows only a few inches in front of the camera is in focus.  

Most consumer priced lenses have a max f-stop of 4.8 or 5.6 and a minimum of 22 or 32.  Some of the high end lenses can get up to 2; enabling some very low light images with out flash.  Settings of 22 or 32 are almost exclusively used in outdoor sunny pictures due to the large depth of field and large amounts of light needed. 

Move your camera's mode selector from 'Auto' to 'A'.  The setting is usually referred to as 'Aperture Priority'. This means the camera will allow you to set the aperture manually while automatically setting the exposure.  This makes it easy for you to use depth of field effects in your pictures. 

Common uses:

Set your camera to f/4.8 for:

    A popular use of this technique is used in wedding photos.  Place the rings on a page with one of the readings from the ceremony.  Set your depth of field so that the rings and only a key phrase from the page is in focus.

    One flower in the field of flowers is in focus, all the others are blurry. 

Set your camera to f/32 for:

    Landscape panoramic where everything from the foreground to the horizon is in focus.

    Preventing over exposure in photos with a long shutter time.  If you were trying to show the blurry waterfall effect on a sunny day, adjusting your ISO may not be enough to prevent over exposure.