Total control is not much good if you don’t know how to use it. To start we need to know that photography is basically controlling light so that the exposure is correct. There are three basic ways to do this from the camera, the shutter speed, ISO and aperture. Each of these control the either the amount of light or the sensibility of the camera and each also has other things it controls.
We are going to start with aperture. Aperture is the size of the opening in the lens. It is measured by f-stops that often can be found on the lens. The higher the number the smaller the opening the lower the number the larger the opening. As you can guess a larger opening lets in more light. So f22 lets in only a little light while f1.8 lets in whole lot more. In fact, standard full stops let in twice as much light as the next stop down. That is to say that f2 lets in half the light as f1.4. Check out Wikipedia for more specifics on this idea.
Ok so aperture lets in more or less light but what else does it do? It controls the depth of field. Of course if you don’t know what depth of field is this information is not all that helpful. Let’s keep it simple, take a look at Alvin, the handsome boxer up top, see how the background is all soft, not in focused. Well, this is a shallow depth of field and it is created by opening the aperture more. This particular photos was taken with an 85mm lens set at f1.8. Now look at the photo below of the woman from Ethiopia. See how the people behind her are not half as soft or out of focus as the background of Alvin. Well, that is a deeper depth of field. It was shot with a 18mm lens set at f9. (Focal length also controls depth of field somewhat but we will talk about that later)
The effect created by different apertures really can change an image as you can see. If you want your viewer to focus on your subject and not be distracted by the surroundings you will probably use a wide open aperture like f2, f1.8, f1.4, f1.2 but if you want the background in focus maybe because it is important to the overall image then you might use an aperture like f8, f9, f11…..
Aperture is not the full story, it is only one part of the equation and it must be mixed with a proper ISO and shutter speed to give you a correct exposure but that will have to wait for another blog post.