The aperture

So you've seen how the shutter is used by your camera to control the amount of light that strikes the image sensor. Now, let's take a look at the aperture. The aperture sits in your lens, not your camera. It's an iris composed of interlocking metal blades. Here is a lens. Watch what happens as the iris is opened and closed. The blades slide back and forth, and as they do so, the hole in the middle can be made bigger and smaller. Obviously, a bigger hole allows more light, while a smaller hole allows less. More light means a brighter image. The size of the hole is specified using a measure called f-stop.

It's a number that refers to the ratio of the size of the aperture to the focal length of the lens. Now don't worry. That's not something you need to really know or think about when you're shooting. All you need to know is that each specific aperture size is denoted with an f-stop number. So, you might have an aperture that's f/4, or f/8, or f/11, and so on. Now this next bit's a little backwards. Bigger numbers mean a smaller aperture, so f/11 refers to a smaller aperture than f/4.

Now one way to think about this is that the iris is stopping light, and a bigger number means more stoppage, which means a smaller hole. Ultimately, as you work with aperture, you're simply going to learn all this by rote. When someone says f/16, you'll know that they're referring to a very small aperture. We're going to be covering apertures and f-stop in great detail throughout the rest of this course. So if this all seems just a little bit arcane right now, don't worry. Just bear with me, and this will get much more clear as we go along.