macro of fountain pen on a book page with shallow depth of field

Aperture

Hi there

Today I thought I would start a series of blog posts to try to explain a few key basics about photography that can change the way you make a photograph forever.

Many people aways use their camera on automatic mode as it gives them the opportunity to literally point and click the shutter button and capture the moment. However, once you are ready to take your camera of the automatic mode it opens up an array of endless opportunities to create photographs how you want. I understand that this is a daunting prospect for many – they see all of the options on their camera and hear about exposure and aperture and ISO and feel completely overwhelmed.In this next series of blog posts I will try to tackle these key fundamentals in hopefully in a simple yet informative way. With a basic understanding of a few of these simple concepts you will be able to start taking real control on how your photographs are made.

Quite simply, your camera records light when you take a photograph. It is this light in various intensities and colors that create your final image. The camera has three key ways for you to control the light that enters the camera, namely; Aperture, Shutter Speed and ISO. For the remainder of this post, I will concentrate on aperture and the next post will explain both shutter speed and ISO and how these controls affect your images. The aperture is another term to describe the size of the hole in the camera’s shutter that controls the amount of light that can hit the sensor when you hit the shutter button and take a photograph. The larger the hole naturally lets in more light and conversely the opposite is true. The size of the aperture is measured on a scale of ‘f-numbers’ or ‘stops’ with (often confusingly) the larger the hole or aperture being reflected in the smaller the f-number.

The f stop scale includes the following common stops:

f1.4, f2.8, f5.6, f11, f16, f22

It is possible to get larger and smaller numbers such as f1.0 and f32 although these are not so common and are usually on more specialized lenses.

So we can see that a small aperture (or ‘f’ number) will let in more light, but it also plays another important role in the camera. It also partially controls what parts of the image are in focus together with the part of the image the you have focussed on. This level of focus relates to the front to back focus in an image rather than side to side. This is known as ‘depth of field’.

The following photographs will show you the concept of depth of field in a simple way:

a photographic example image showing  depth of field and an aperture of f2.8

a photographic example image showing depth of field and an aperture of f2.8

In the first photograph above the camera was focussed on the stone with the line and was taken in a large f number (f2.8) giving a small depth of field. You can see that the 2 stones in front and 1 stone behind are all blurred and out of focus although the stone with the line is clear and in focus.

In the next image, I have still focussed on the same stone with the line, but changed the f number to f11. You will see that the 3 other stones are still blurred but not to the extent of the above image.

a photographic example image showing  depth of field and an aperture of f11

a photographic example image showing depth of field and an aperture of f11

In the final image below, taken at f22, you can see that the stones are all much more in focus when compared to the first and second picture above, (although they are not all completely in focus).

a photographic example image showing depth of field and an aperture of f22

a photographic example image showing depth of field and an aperture of f22

So you can see that changing the aperture will not only increase the amount of light in a photograph but also to control the depth of field within the photograph itself. This technique enables you to draw your viewers eyes to a particular place in your photograph that you want to emphasize – such as the stone with the line in the first picture above. Using a shallow depth of field also allows you to ‘isolate’ particular parts of an image and separate them from a busy or distracting background. Here are a few examples of this:

close up of a yellow dragonfly with shallow depth of field

close up of a yellow dragonfly with shallow depth of field

macro of cherry blossom flower with shallow depth of field

macro of cherry blossom flower with shallow depth of field

macro of fountain pen on a book page with shallow depth of field

macro of fountain pen on a book page with shallow depth of field

cabbage butterfly with purple thistle flowers in shallow depth of field

cabbage butterfly with purple thistle flowers in shallow depth of field

Although sometimes you want to ensure that the whole image is in focus from the front to the back (such as in a landscape photograph) and as such you will want to use a smaller depth of field by choosing a larger f number.

For example:

Lone tree in a lavender field with a stormy sky landscape with deep depth of field

Lone tree in a lavender field with a stormy sky landscape with deep depth of field

London Tube subway train station walkway with deep depth of field

London Tube subway train station walkway with deep depth of field

I hope that this gives you a basic understanding of the principles of aperture control and how you can use this to create different effects in your photography. It is definitely worth trying for yourself and experimenting with the results. Most cameras have an aperture priority mode (on Canon cameras its the symbol ‘AV’ on the control dial and ‘A’ on Nikon cameras). Just remember that the larger aperture has a smaller f stop number and will give you a more shallow depth of field and blur and conversely the smaller aperture has a larger f stop number giving you more depth of field.

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