Working With Aperture

As we discussed, exposure is partially controlled by the aperture setting on the camera.  Aperture settings affect far more than exposure, however.  It also controls the depth of field, which means just how far away the camera's eye can see and record sharply.  There are times when you want great depth of field and others when you want to blur a distacting background with a shallow depth of field.

Depth of field can also be referred to as the number of f-stops.  To be technical about it, each f-stop doubles the amount of light that reaches the camera's sensor when going from the smallest to the largest and likewise halves the amount of light when going from the largest to the smallest.  The thing that tends to be very confusing is that the size of the aperture does not correspond to the number system.  F-22, for example is the smallest aperture size and has the greatest depth of field.  F-5.6 is a much larger aperture opening and produces a shallower depth of field.

Aperture settings

So, just what is the purpose other than affecting exposure, does changing the aperture setting have on your shot?  As mentioned in the first paragraph, it controls the degree and distance in which a photograph will be sharp or in focus.  A smaller aperture, f-22, for example will result in a scene that is sharp at a distance and close up.  A larger aperture will result in a blurred or out of focus background, but a sharp foreground.  Not all cameras respond the same way to changes in aperture settings, so be prepared to experiment to learn how your specific model responds.  The type and size of the lens will also restrict the size of the aperture you'll be able to work with, so the fiull range of stops may not be available for use.

Changing the aperture settings depends on your specific camera and you will need to refer to your manual.  Most DLSR's, however, have a dial on the top of the camera.  Look for the "A" and turn it to place the camera on the aperture mode.  As you change the number of f-stops per the instruction manual, the camera will automatically adjust the shutter speed to compensate.

Assignment

Find a specific object, not a busy scene but one or two focal points, such as a flower in a garden.  Using different aperture settings, take a number of shots of the same thing.  This will let you compare the differences far more easily.  You can certainly do the same thing with a landscape shot, but you may not be able to compare easily unless you include something in the foreground for the camera to focus on as well. Make sure you include both a small and large aperture and view on full screen.

Upcoming

Shutter speed and chang the look of a moving object.