Fortunately photography talk is a lot easier than French and physics. And best yet…there are no verbs to conjugate or mathematical equations to puzzle through.
Aperture really is an easy concept to learn. It relates to the amount of light that travels from the lens to the film or digital chip. Think back to biology and the human eye. In dim light, your pupil dilates so that most of the colored part of your eye looks black. That allows for more light to hit your retina, and allows you to see what’s in front of you before you stub your toe. In bright light, your pupil shrinks to cut down on the amount of light that hits the retina. In photography terms, the camera lens works like the pupil. The film and digital chip are similar to the retina.
For most camera lenses, the aperture ranges between 4.5 to 32. Faster—and subsequently more expenses lenses—go down to 2.8. The smaller the number, the wider the lens opening, and thus, the more light that hits the digital chip—or film. When you select a larger number, the amount of light that hits the digital chip is much less than before.
So what does this have to do with your photos? The depth of field effects how much of your subject and the surrounding area—both in front of and behind the main point of focus—will be clearly seen. A piece of paper is two-dimensional. It can be thought of as having a shallow depth of field—okay, an extremely shallow depth of field. In this example, a cardboard box would have a wide depth of field. If you adjust the aperture to a lower number such as 4.5, your depth of field will be limited. Everything behind and in front of the subject will be blurry. If you adjust the aperture to 32, the depth of field becomes wide and everything in the picture will be in focus, which is why this setting is perfect for landscape photography.
In the above two photos, I focused the camera on Stephenie Meyer’s Novel, Eclipse. I set the aperture to 4.5 for the top photo, and increased it to 32 for the bottom one. Do you see the difference?
Are the numbers between these two extremes really important? Yes. There are some subjects that do better when taken in the middle range. Experiment with a variety of apertures on different subjects, and see for yourself the benefits and disadvantages of both.
And one final point. Usually, so you can see clearly in the viewfinder, the camera is automatically set at a wide aperture (small number) before you take a picture. This allows in more light so you can see the image you’re shooting. It also means that if you’re using a small aperture (large number), your friend might develop a tree growing out of her head that you hadn’t seen before taking the photo. Some cameras have a preview button; otherwise, you’ll need to check out the subject and surrounding area with the naked eye before taking the picture. If you’re using a digital camera, it isn’t as big a deal as compared to with film.