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Exposure : Aperture : Shutter Speed : ISO : Composition : White Balance : Flash : Mega pixels


The aperture (f stop) not only effects the amount of light entering the camera, it also determines how much of the subject is in focus, this is known as ‘depth of field’.

Aperture F22 F4

The smaller the aperture (F16) the larger the depth of field, you will have to compensate with a slower shutter speed.

larger the aperture (F4) the shallower the depth of field, also known as selective focus, you will have to compensate with a faster shutter speed.

F5.6 Shallow depth of field. ..... F16 Large depth of field.

Shallow depth of fieldmaximum depth of field

We can see that the use of ‘selective focus’ is an excellent device for separating something from a distracting background (f5.6)

For most occasions when you want everything in focus you use the smallest aperture available (f16 / f22)

There are a couple of things to remember:

1. The depth of field increases the further away an object is, so selective focus only really works on close up objects.

2. For each stop you adjust the aperture you need to compensate with the shutter speed i.e. as you increase or decrease the size of the aperture / hole you need to shorten or lengthen the shutter speed by the same amount of

canon mode display

On older cameras the aperture used to be set by turning a ring on the lens, on DSLRs it will be linked to the A or Av setting, and a dial you can turn with your finger, whilst looking through the viewfinder.

Try setting the mode of your camera to A / Av mode, make sure you are in a bright place and turn the control dial until the aperture number changes, notice how it automatically changes the shutter speed for you to maintain the right amount of light entering the camera.

camera mode dial
Many professional photographers I know use the A setting on their cameras, you maintain the control but the camera does the hard work of ensuring the light balance is correct. But when you want to take full control, the manual mode is still something you should know how to use.

© Nigel Watts 2011-2016 Contact/About