Aperture: A basic explanation for beginners

Focus and light

 Photography is a science of light. How much light, for how long, and from where, determines the exposure of your image. And exposure is the the base of your image. There are loads and loads of explanations of aperture, shutter speed, and iso and how they affect exposure. I cover Basic Exposure in my post Basic Exposure for Beginners. Here is my take on APERTURE. 
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Aperture is set in f stops. Aperture goes as wide open as 1.2 and as closed 32. The aperture you are able to shoot with will vary depending on the lens. The wider open the aperture, the more light gets in to your camera for the image. Conversely, the smaller the aperture, the less light will get in to your to you sensor. Each FSTOP higher closes the hole smaller and smaller. It can get kind of confusing when starting out, because people may refer to using a "large" aperture meaning they used a small f-stop number which makes for a larger opening. F 1.8, which is the most open setting on my favorite 50mm prime lens, is as large an opening as that lens will open. The graphic above actually starts in the upper left corner with a "higher" or smaller aperture f stop, and ends in the bottom right corner with a "lower" or smaller aperture. 

Aperture and focus

Aperture basically determines how at what distance your lens will focus and how far it will focus. For example, If you are shooting a your kids in front of the Grand Canyon, you probably want your kids smiling faces in focus and a large portion of the Canyon, too. You want to be able to see where your kids were at the time of the picture. A smaller opening in the aperture  will make for a longer depth of field. And remember, smaller aperture means larger number when changing your settings. 

Lower f stop numbers mean a shorter depth of field. Which in the example above would mean that your kids faces would be in focus, but the background behind them would be more and more blurred the further away they were from the subject.

Below I  have some examples, where the only setting I changed was the aperture or f stop. Notice the subject is the dark duck. I wanted these pictures to have the back lighting so it would stick out how the background was being blurred and sharpened using the aperture. I didn't worry about lighting my subject at this point. 

I shot these with a kit lens 18-55mm becuase I wanted to use a lens that a beginner would most likely have. You can see an even stronger difference with lenses that will open up to larger apertures. All settings stayed the same except adjusting aperture. Notice the stronger difference in the lack of focus of the background from image one, to the more focused back ground of image 6.

Aperture and light. 

You will probably notice, that when the aperture is larger larger, the image lightens. That's because more light is getting in the camera. This is one of the ways you can lighten your image in dark situations, just keep in mind that this blurs objects and scenery that are not the same distance from your camera, because it shortens the depth of field. 
The opposite is also true, by decreasing the size of the aperture, I can decrease  the amount of light on a bright sunny day. However, this would not be the optimum way of doing this by itself if I were taking portraits or wanted a nice bokeh, because it will also bring my my background into clearer focus.

While not a beautiful image, I have done NO editing to this picture at all. It is a good example of a very short depth of field and how aperture affects depth of field. 

My focus is on the leaf and grass just to the right and below the center of the picture. By having the aperture at 1.8 (as wide open as my 50mm lens will go) it gives a very short depth of field. The background and the foreground have pretty good bokeh or blurred effect. If I were shooting a landscape I wouldn't want this blurred  effect. But, for portraiture it can draw your eye into your subject. 

What did you like? What was confusing? What are you ideas? Let me know!