Introduction to Aperture in Photography-Part I
Without a doubt, aperture is the most important of the three camera settings, simply because it affects so many different variables of an image. It can add dimension to your photographs by blurring the background, and it also alters the exposure of your images by making them brighter or darker.
By adjusting your Aperture, you can change the depth of field in an image, as shown here. 
What is Aperture? Aperture is a hole within a lens, through which light travels into the camera body.
How Aperture Affects Exposure
Aperture has several effects on your photographs. One of the most important is the brightness, or exposure, of your images. As aperture changes in size, it alters the overall amount of light that reaches your camera sensor – and therefore the brightness of your image. A large aperture (a wide opening) will pass a lot of light, resulting in a brighter photograph. A small aperture does just the opposite, making a photo darker.
Aperture Effect on Brightness
In a dark environment – indoors, or at night – you will probably want to select a large aperture to capture as much light as possible.
How Aperture Affects Depth of Field
The other critical effect of aperture is something known as depth of field. Depth of field is the amount of your photograph that appears sharp from front to back. Some images have a “shallow” depth of field, where the background is completely out of focus. Other images have a “large” depth of field, where both the foreground and background are sharp.
One trick to remember this relationship: a large aperture results in a large amount of background blur. This is often desirable for portraits, or general photos of objects where you want a blurry background.
So far, we have only discussed aperture in general terms like large and shallow. However, every aperture can also be expressed as a number known as an “f-stop.” Whenever you see an aperture value, the letter “f” will appear before the number, like f/8.
Most likely, you have noticed this on your camera before. On your LCD screen or viewfinder, your aperture will look something like this: f/2, f/3.5, f/8, and so on.
Stay tuned next column for additional tidbits on aperture and how it plays an important part in photography.
