1. Shooting modes

The best place to start is with shooting modes.  The shooting modes will most likely be found on a dial labelled with ‘auto, Av, Tv, P, M’ and maybe more.  Selecting a shooting mode will determine how your camera behaves when you press the shutter, for example, when ‘auto’ is selected, the camera will determine everything to do with the exposure, including the aperture and shutter speed.  The other modes, ‘Av, Tv, P, M’, are there to give you control:

Don’t worry if your mode dial looks a little different; different manufacturers use different abbreviations for the shooting modes.  Your mode dial may have the letters ‘A, S, P, M’ (instead of Av, Tv, P, M), yet they all function in the same way.  Below, I have given each abbreviation for the given mode.

Aperture Priority (Av or A)
Aperture priority can be thought of as a ‘semi-automatic’ shooting mode.  When this is selected, you as the photographer set the aperture and the camera will automatically select the shutter speed.  So what is aperture and when would you want to control it?

The aperture is the size of the opening in the lens through which light is allowed to pass whenever the shutter is opened – the larger the aperture, the more light passes through.

The aperture is measured in ‘f-stops’ and is usually displayed using an ‘f-number’, e.g. f/2.0, f/2.8, f/4.0, f/5.6, f/8.0 etc, which is a ratio of focal length over diameter of the opening.  Therefore, a larger aperture (a wider opening) has a smaller f-number (e.g. f/2.0) and smaller aperture (a narrower opening) has a larger f-number (e.g. f/22).  Reducing the aperture by one whole f-stop, e.g. f/2.0 to f2/8 or f/5.6 to f/8.0, halves the amount of light entering the camera.

Aperture is one of the most important aspects of photography as it directly influences the depth of field – that is, the amount of an image that is in focus.  A large depth of field (achieved by using a small aperture (large f-number)) would mean that a large distance within the scene is in focus, such as the foreground to the background of the landscape below.

An aperture of f/13 was used here to give a large depth of field, ensuring that the whole image, from the foreground grasses to the background mountains. was sharp

Whereas a shallow depth of field (achieved by using a large aperture (small f-number)) would produce an image where only the subject is in sharp 

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