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  • Nigel

Aperture. So that's how it works!

The great thing about photography today is that you can get excellent results by setting the camera to ‘A’ (automatic) leaving you to concentrate on the subject. However, if you understand a little bit about the other settings, you will widen the scope of your photography and be able to control your results.

I am going to start off with a brief look at aperture, speed, sensitivity (ISO), and focus. One per blog!


Light enters the camera through the hole at the front, the aperture! So far, so simple. But then we hit a problem. How do we measure the light coming into the camera? It’s easy now because we have in-camera exposure meters but not so long ago we had to ‘guess’ the brightness. The ‘f’ stop was invented to let photographers adjust the exposure independently of the camera or lens.

‘f’ stop ( a bit of maths, sorry)

The ‘f’ stop is the ratio of the diameter of the aperture to the focal length (distance from the hole to the sensor(film)).

N= f/d

(N: f number f: focal length of lens d: diameter of aperture)

This gives a rather awkward set of numbers… but at least they are the same for all cameras and lenses. So we don’t go bonkers, camera manufacturers have decided to choose certain ‘f’ stops to mark on lens or to show on the camera body. These are:

1.4, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.00

Shine a light

1.4 lets in more light than 2.8. 2.8 lets in more light than 4.0.

In fact, each of the values lets in twice as much light as the value to its right, and half as much as its neighbour to the left.


Big aperture <<<<< >>>>>Small Aperture

Used in dark conditions to let in more light <<<<< >>>>> Used in bright light

F1.4 <<<<< >>>>> f 22


Aperture and focus

Of course, if that was all there was to it, then it would be easy. But the aperture also affects focus and that’s where we can get creative with it. I’ll cover this later in detail but broadly:


Big Aperture (f2.8) <<<<< >>>>> Small Aperture (f16)

Not much in focus <<<<< >>>>> Everything in focus


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