So you bought a DSLR camera and have it set to Auto, because you have no idea what any of the settings on the top dial mean, right? This article is the first step in taking creative control of your images and not letting the camera choose what IT wants your image to look like.
What is Aperture? What is Aperture Priority? Your Aperture is the diaphram(hole) in your lens that opens wide or shrinks small to let light into the sensor. It also controls your depth of field, or how much of the picture you want in focus.
Lets say, you want to take a portrait shot of someone, and you want them to be sharp, but you want that beautiful, blurry background(called bokeh). How do you get that look? You simply adjust your aperture so that the hole in the lens is wider or larger.
Aperture is measured in F stops. You will see numbers like f/1.8, f/2.8, f/4, f5.1, f/7.1, f/8, f/11, f/16, f/22, etc. What you need to know is this; the smaller the number, the larger the aperture. So in my examples, f/1.8 would be the widest aperture, and f/22 would be the smallest. So if you want that blurry background, or, in photography terms, shallow depth of field, you want your aperture at f/1.8. Conversely, if you are taking a landscape photo and want all of the photo in focus, or in photography terms, greater depth of field, you would set your aperture to f/22. As you make your way from f/1.8 to f/22, the depth of field begins to change, making more and more of the picture come into focus.
Now, most kit lenses that come with your new DSLR have a minimum and maximum aperture. Usually they start at f/4, and go up to f/22. Some will vary in minimum aperture as well. For example, a Nikon 18-55mm kit lens that comes with a Nikon D3300, will say something like this; f/3.5-5.6 or on the barrel of the lens, 1;3.5-5.6. That simply means that at the shortest focal length of 18mm, the minimum aperture is f/3.5, and at the longest focal length of 55mm, the minimum aperture is f/5.6. The more expensive, higher end lenses have a constant minimum aperture throughout the focal range.
Now lets get into taking our camera off of Auto! Lets put it into whats called Aperture Priority mode. Turn the dial on top of the camera to "A" or "Av." This is a semi-auto mode that lets you control the depth of field, while the camera then determines the shutter speed based on its meter. Now you can adjust the aperture from its lowest number up to its highest, take some shots and experiment with that depth of field. Boom! You have taken your first step in taking creative control of your images! Now go out and get some shooting in, and come back to read the next article on Shutter Speed, and Shutter Priority.