Aperture, Shutter speed and ISO Explained

The beginning of a new year seems like a good time to think about starting out in photography – and how daunting and confusing some of the photographic jargon can seem when you first begin!

So today I thought I would have a look at some of the basic terms that you might come across.

Aperture I remember that when I bought my first SLR camera, the aperture settings were one of the most baffling things to me. These settings are also known as f-stops, and are represented by a seemingly bizarre series of numbers, which on a typical lens might include f/2.8, f/4, f/5.6, f/8, f/11, f/16 and f/22.

Wikipedia defines the standard f-stop scale as “an approximately geometric sequence of numbers that corresponds to the sequence of the powers of the square root of 2”. But luckily, it’s not necessary for us photographers to understand this geometric sequence. What we do need to know is this:

· The aperture is a hole in the lens which allows light through to hit the digital sensor

· A small hole will only allow a little light through, a large hole will allow much more light through

· The aperture setting controls the amount of light which enters the camera through the lens

· The lower the f number, the wider the aperture

· The higher the f number, the smaller the aperture

· Changing from one f stop to the next one will either double or halve the amount of light entering the camera

The aperture setting also controls the depth of field in a photograph – for more about this, see my blog on August 20th.Shutter speed This is another series of numbers that expresses how long the shutter in your camera remains open to let light into the camera. These numbers are expressed in seconds, or fractions of a second. A one second shutter speed will allow twice as much light into the camera as a ½ second shutter speed, four times as much as a ¼ second shutter speed, and so on.

If you are photographing a moving object, the choice of shutter speed will also affect the appearance of that movement in the photograph – in general, a fast shutter speed (maybe 1/125 sec or faster) will freeze movement, while a slower shutter speed will show movement as a blur in the resulting image.

If you use a slower shutter speed, you may be in danger of camera shake – in this case you will need to use a tripod for stability during the exposure.

For more about shutter speed, see my blog on October 15th.

ISO Another series of numbers ranging from 100 ISO upwards. These numbers express the sensitivity of the sensor to light, with the lower numbers being less sensitive than higher ones. For more detail on this, see my blog on October 3rd.

The combination of the aperture and shutter speed settings, together with the ISO setting, are used to determine the exposure for your photograph.For more detail about this, see my blog on September 21st.

It seems like a lot to take in at first – but once you understand these basics, you can really take control of your photography instead of letting the camera take control for you!