Now that you have a good idea of how exposure can affect your pictures, you need to get more in depth details on how to control that exposure. As mentioned before, there are two settings that will affect the exposure of your image. These two things will be aperture and shutter speed. Let’s talk about aperture now.
When your camera lens takes a picture, it lets light through an opening in that lens. This opening can be changed to allow different amounts of light. This change in the opening on the lens is referred to as the aperture. There are two different ways that people refer to this setting and you may hear it referred to as either interchangeably, so do not get confused. If you hear someone refer to the f/stop on the camera, this is exactly the same thing as aperture.
As you can imagine, if the camera lens is open very wide, it will allow a great deal more light and will allow more exposure for the image. If the lens is smaller, then it will allow a smaller amount of light. To understand the f/stop, think of it as directly opposite of the lens width. The f/stop will either be high or low. A high f/stop will offer a narrow aperture. A low f/stop will offer a wide aperture.
One thing that is very interesting is that aperture will have more affects on the image than just the amount of light let into the camera. Aperture will also affect the depth of field in the image. Just what is depth of field? This has to do with what part of the image is in focus in your picture, and the more you can control the depth of field, the more artistic and beautiful your pictures can be.
To get a good idea of what depth of field, take a look at a really good portrait of someone. Do you notice how the person in the picture is clearly in focus and the background is blurry? This is achieved with depth of field and aperture. If you use a wide aperture (and therefore a low f/stop), this will allow a shallow depth of field and your background will be blurry. This is very useful if you are taking a picture of a person or a specific item like a this baseball in the grass.
If you are taking a picture of a landscape or a building or you simply want everything in focus, then you will need a narrow aperture (and a high f/stop) so that your camera will be able to focus on everything.
The more you can learn to control the aperture on your camera, the more detailed and artistic you can make your pictures look. Being able to control these things will take you from an amateur photographer to a semi-pro.