Apertures and Depth of Field

Words and photography by Paul Worsley

Apertures have an incredible amount of influence over how a picture looks and also how well it is exposed. Depending on the image taken and what you want to achieve, this powerful camera tool can work hand in hand with other camera operations.

Lets start with apertures. Imagine a circular eye in your camera that can open wide or close down as small as a pinhead. This will control the amount of light that passes through. It also controls the depth of field. Depth of field is basically how much of your image stays sharp from your point of focus. The smaller the aperture is, eg. Pin head, the sharper your image will be throughout. Thus, the larger your aperture the less will be in focus. I remember this by imagining that when you squint your eyes you seem to be able to see further and clearer. Smaller apertures are generally used more for landscape shots and the type of shot where you want to see the whole subject pin sharp. Larger apertures are used more for portraits, (background blur makes the subject really jump out at you) or even arty shots of food and other things.

The important thing to remember is, small number eg. F4 means wide aperture. Large number eg. F22 means small aperture. For optimum lens performance, f8 is usually the best.

If it’s a dark and cloudy day, smaller apertures are more of a challenge because of less light entering, so this is where you have to work closely with other camera functions to allow for this. Film speed or ISO and shutter speeds are the two we will go into in detail next month. Happy snapping!!