Photography is all about capturing light. The skill is in capturing the light in such away that the image can be accurately reproduced later. Pressing the shutter button on your camera allows light to pass through the aperture and onto the sensor. The duration the shutter is open for (shutter speed) and the size of the aperture have the most profound effect on the final result.
Getting the shutter speed right is the most important aspect of taking a picture. The shutter on your camera determines how much light is allowed to reach the sensor. A faster shutter speed equals a longer exposure. But what does exposure mean? Exposure literally means the time for which the sensor is exposed to the light.
If your shutter speed is too slow the picture will be over-exposed and detail will be lost.
In this picture the shutter speed was too slow resulting in over-exposure. If your shutter speed is too slow then the picture will be under-exposed and again detail will be lost.
In this picture the shutter speed was too fast resulting in under-exposure
A camera's aperture is the hole in which the light passes through to reach the sensor. A wide aperture is a big hole, a narrow aperture is a small hole. But how does this effect the picture? This is where it gets a bit complicated. I will try my best to keep it simple and to be concise.
Your camera's aperture settings are displayed as an f-number? f-number is calculated by dividing the focal length (distance from the lens to the sensor) by the size of the aperture.
Focal Length/Aperture = F-number
What this essentially means for the beginner is a low F-number is a big aperture, a high F-number is a small aperture.
A wider aperture allows more light through to the sensor than a smaller aperture does. This means that when taking a picture of a subject using a wide aperture, a shorter exposure (faster shutter speed) is required than when taking the same picture with a narrower aperture.
However this is not the only effect that the aperture has on the final picture. A wide aperture will decrease the depth of field of the image. Conversely a narrower aperture will increase the depth of field of the image.
Left: f 5.6, 0.6 seconds Right: f 36, 25 seconds
The example picture above demonstrates the effect of aperture on depth of field. The Picture on the left was taken with a wide aperture (f5.6) and a shorter exposure. The picture on the right was taken with a narrow aperture (f36) and a longer exposure
It is clear to see that the wider aperture picture (left) has less depth of focus than the narrower aperture picture (right).
A common problem for beginners is getting the right balance between depth of field and exposure. If you wanted to shoot an action shot with a deep depth of field the exposure would be too long and the resulting picture would be blurred. Conversley if you wanted to freeze the action with a high shutter speed you may end up with a too narrow depth of field resulting in parts of your subject being out of focus. There is a saying among sports photographers 'f8 and be there'.
N.B: The maximum/minimum aperture you can use is determined by your lens, NOT your camera.
So now we (hopefully) understand the effect shutter speed and aperture can have on the final image. Let's move on to the next guide to learn how to set our camera's aperture or shutter speed.