So far I have covered shutter speed and sensitivity. In this blog I am going to explain perhaps the most complex aspect of photography - aperture.
Put simply, aperture is a measure of how wide the iris of the lens is. This measurement determines how much light reaches the sensor. Just as the iris of your eye is where light enters, the iris of a camera lens is a series of blades that form a hole for light to pass through. In low light, the iris of your eye expands in size to allow more light to enter and in bright light it dilates so that your are not blinded. The same principal can be applied to a camera iris. The more light you want to enter the sensor, the wider the iris needs to be and vice versa.
Aperture is measured in f-stops. The wider the aperture of the lens, the smaller the f-stop. For example f/1.2 would determine a very wide aperture, almost entirely open; while f/22 would determine a very small aperture with the iris almost entirely closed. Setting your aperture from one stop to the next doubles or halves the opening of the iris and therefore the amount of light entering the lens. At this point it is worth noting that changing your shutter speed from one setting to the next has the same effect so decreasing one and increasing the other means you will let in the same amount of light. Knowing this can allow you to achieve the desired effect.
As well as controlling the amount of light that enters the lens, the aperture also has an effect on the amount of your image that is in focus. This is called the Depth of Field. The more light that enters the lens, the shallower the depth of field will be. As a result of this an f-stop of f/1.2 will have an extremely shallow depth of field, perhaps only centimetres or even millimetres of focus. Conversely an f-stop of f/22 will have a very deep depth of field with only the very furthest objects out of focus and even then only slightly. When understood and used correctly, aperture allows you to produce some beautiful images and can really help set your photography apart.
Some styles of photography require very specific apertures but I will go into this in posts related to those styles.