Ever notice your lens has this "eye" that looks at you? Sometimes it opens up wide and sometimes it's very small. Well, this is your lens opening up wide and small to control the amount of light that enters the lens. This is called the aperture. It's one of the three factors that make up the exposure triangle. Shutter speed and ISO make up the other two areas but we'll save those for their own posts.
The aperture is measured in stops or F stops. The wider the eye opens the lower the number is. For example, f2.8 is very wide open allowing a ton of light in. Whereas, f22 is extremely small, allowing minimal light in. As this is adjusted the depth of field changes. Example, the lower the f stop, (i.e. f1.4) the more shallow the depth of field gets, which means les of the scene is focused. When you see those awesome photos with a person that is very focused but everything behind that person is out of focus and very blurry, that is due to a shallow depth of field. The higher the f stop (i.e. f20) the more in focus objects in the scene will be such as the foreground, background, etc.
Notice how much is in focus with the first photo shot at F20 aperture (higher depth of field). The bananas, chair, windows, etc.
Now, look at the below photo shot at F2.8 aperture. Only the banana and flower pot are in focus due to the shallow depth of field. That blurry background is referred to as bokeh and it provides that soft blurriness that we all love that helps the primary subject standout.
Alright, I hope I connected some dots for you and aperture makes a little more sense to you. I'll follow up on the two other factors that make up the exposure triangle in future posts. Travel. Hike. Click!
The Lost Photog