Mark and I are on a quest to get any beginners off the “P,” or program mode, on their camera. If you’re one of those people, don’t run from the room. You will not have to become a photogeek to understand this stuff. I’ll make this short and sweet, and I promise to type slowly. (OK, that was childish and uncalled for…) I’m just teasing….c’mon back. Setting your camera on P means you leave all the decisions for your image in the hands of your camera. Aside from automatically focusing your camera, there are three important settings your camera will make without your input: ISO (sensitivity to light); shutter speed; and aperture (a measure of the amount of light passing through the lens). The default settings are usually the lowest ISO, highest speed, and smallest aperture possible. Different manufacturers use different algorithms to achieve their solutions, and your camera “scene” settings affect the final answer. For general photography, this work pretty well most of the time. What if you want to make pictures that don’t use the cameras defaults? How can you control the final outcome of a picture? Change some of the automatic settings that impact the image. Move your camera setting away from the P setting.
Today, we’ll do a quick discussion about selecting your own aperture and why learning how to use it gives you more control over your photos. Aperture refers to the lens diaphragm opening inside a lens. The size of the opening determines how much light passes through to the sensors (or film, for those that still use it) inside the camera when you press the shutter release. Cameras measure this in f-stops. (Don’t ask me why; I’m trying to keep this fairly simple.) If you use a point-and-shoot and can change this setting, you’ll see the f-stop setting on your rear display. DSLR camera owners will see the f-stop in their viewfinder and on the outside of the lens barrel. Just to complicate things, the f-stop numbers (f2.8, f4, and up to about f32) seem counter-intuitive because f2.8 actually allows in more light than f4 and so on. The numbers all make sense if you go further in depth on this, but we’re not going there today. Mark can go into the math calculations in his head, but that scares people. I understand. I have a liberal arts degree, so you won’t hear that from me. I can’t promise that he won’t do it, anyway, but that will be another day.
The most important reason to change your aperture settings is to impact your depth of field. The smaller the f-stop number you set, the wider the diaphragm is opened, the more light that gets in, and the narrower the depth of field in your photo. Depth of field affects how much of your photo is in sharp focus. You thought all of the picture should be in focus? Well, not necessarily. You’ve seen many photos that blur parts of the image (usually the background) to direct the viewer’s eye to what the photographer’s main subject. There is much more to this subject, but the goal here is to explain the effect. If you understand the effect, you can use it to control your images.
Here is an example of how changing the depth of field can affect an image. Notice, as the f-stop number is increased, more of the pool balls are in focus. The 9 ball is my focus point (and, yes, I need to brush the table). The other balls are further away and out of focus, but as the f-stop number is increased and the depth of field is increased, they begin to come into focus.
And here is a much prettier example of why a narrow depth of field has its place in your photography. The eye is drawn to the face which is in sharp focus, which was my intent. Notice her shirt and shoulders are already losing focus, and the building and trees are completely blurred. Now go have some fun adjusting your aperture while you take photos.