Photography Tips- What is Aperture?

The Aperture and Light:

If you look at your SLR camera lens you will most likely see two sets of numbers. The particular set we’re going to be talking about here in regards to aperture will have numbers in the sequence 2.8, 4, 5.6, 8, 11, 16, 22, etc. These numbers are called your F-stops. If you’ve read my article on shutter speeds, I defined the term stop as a measure of exposure. Stop is more accurately used in regards to aperture, as it describes aperture size. Aperture is essentially the size of your lens opening. If you think about the pupil of your eye, you’ll recall that it expands and contracts in order to let in more or less light. The aperture is actually a ring within your lens that widens or contracts depending on the settings you choose (i.e. the ring with the f-stop numbers I mentioned). When you remove your lens from your SLR camera, you can actually see the ring that adjusts. If you like, you can adjust those numbers I mentioned while the lens is removed from your camera, and you will see the ring open and close. Here is an idea of what aperture looks like:

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What do the F-Stop numbers mean?

If you remember my article on shutter speeds, I explained that the shutter speed measurements (100, 200, 400) are actually fractions of seconds (i.e. 1/100s, 1/200s, 1/400s), which means the higher the number, the FASTER the shutter. The same applies to F-Stops. F/22 is actually a measurement of 1/22 , which means the lens opening is going to be SMALLER. F/4 will actually be ¼ and therefore be a wider opening.

Why is aperture important?

Aperture controls two things: exposure and Depth of Field. Depth of Field is how much of your photograph is in focus, from foreground to background. With f-stops you can soften that background in a portrait or make that landscape you love in almost complete focus, but you have to know how to adjust aperture to your desired effect. Aperture controls exposure by allowing MORE light in on a lower f-stop setting, i.e. f/2.8. This is because the f-stop is actually a wider opening, since it’s a larger fraction. Makes sense, right? Well here’s where it can get backwards and confusing. This same setting of f/2.8, when compared to f/22, is actually going to give you a smaller depth of field, meaning only a small portion of your photograph is in focus. I will discuss Depth of field more, later. For now, here examples of how aperture affects depth of field:

f/22

f/3.5

So let’s recap:

-Aperture is a ring in your lens that contracts or widens based on the f-stop settings you choose.
-F-stop is a fraction that represents how large the opening is in your lens, which directly affects how much light is reaching the film/digital sensor.
- Aperture also controls depth of field, which is the area of your photograph that is in “acceptable” focus. “Acceptable” is a loose term, but essentially means how much of your photograph (from foreground to background) is in focus.