Aperature - What is it, and how does it affect my photos?

Aperature - The measurement of the circular opening by which light comes from the front of the lens through to the image recording surface (i.e. 35mm negative film, or a digital camera's CCD). Aperature is measured in "F Stops".

Unfortunately, this gets a little confusing because the larger the measurement, the smaller the diameter (i.e. the less light that comes through). For example, an aperature setting of f/2.8 is a much larger size diameter than is f/16.

The F Stop values for aperature are f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128, etc. Some cameras will let you set the aperature in 1/2 stops or 1/3 stops. On a camera that allows 1/3 stop settings, for example, you might see a series of values between f/5.6 and f/8 as f/5.6, f/6.3, f/7.1, f/8.

Aperature has it's biggest impact on what's known as Depth of Field. This is the vertical distance in front of the camera that will appear in focus in the final image. As a general rule, the larger the opening for light (i.e. the smaller the F Stop value you use), the less of your scene that will be in focus. If you want to isolate your primary subject in a photo by having them clear, but everything else in front of and behind them out of focus, then set your aperature value to a very low F Stop. This blur effect is known as "Bokeh". A lens is said to have good bokeh if it can smoothly blur the background of a shot when using low F Stop value for the exposure.

The other consideration for Aperature is how it affects your shutter speed. In sports photography or low light situations, you will often want to get your shutter speed as high as possible. The lower you set your aperature F Stop value, the more shutter speed you will be able to get as a result. Of course the trade-off is that your background will be more blurred the lower you set your aperature, but getting a higher shutter speed is often worth the trade-off.