When you’re learning to get your camera “out of auto” and manually define your camera’s exposure settings, one of the first things you’ll need to master is aperture and the associated f-stop setting. You may be asking, what is an f-stop?
This article will define f-stop and explain how you will use f-stops in your photography. We’ll list the common f-stops on the aperture scale and describe how different f-stops affect your photographs. Understanding f-stops is so important, the things you learn in this guide can help you become a better photographer.
What is aperture?
Aperture is an opening in your lens that allows light to pass through it and into your camera. When you press your camera’s shutter release button, that hole opens to allow whatever scene you’re shooting to be ‘seen’ by your camera’s sensor. While this article is focused specifically on f-stops, we’ve written a very detailed article about all the aspects of aperture that you should check out by clicking here.
What is an f-stop?
An f-stop (also known as an f-number) is the ratio of the lens’s focal length to the diameter of the opening in the lens. While this may sound very technical, a very simple way to explain an f-stop is to say it’s the number that shows when you change your lens aperture.
We use f-stops instead of actual aperture measurements for consistency and ease. Otherwise, apertures would be different from one size lens to the next.
It’s essential to understand how apertures and f-stops relate to each other because this can be very confusing for beginning photographers.
First, think of the pupil of your eye. When you’re in a bright room, your pupil contracts, or gets smaller, to let in less light. When you’re in a dark room your pupil will enlarge to let in more light. Apertures work the same way.
Now, here’s where it gets tricky. The smaller the f-stop or f-number, the larger the aperture. On the contrary, a larger f-number indicates a smaller aperture. Why? This is one of the most important things to understand about f-stops—they are actually written as fractions.
The “f” in f-stop stands for focal length. So, an f-stop is a fraction of the lens’s focal length.
Think of f/2 as the fraction 1/2. Now think of f/16 as 1/16. If you know anything about fractions, you know that 1/2 is much larger than 1/16. Based on that, you’ll also know that f/2 is a much larger aperture than f/16.
So, to recap:
- Large, or wide, apertures let more light in. Indicated by a small f-number;
- Small, are narrow, apertures let in less light. Indicated by a large f-number;
- A medium aperture falls somewhere in between. Indicated by a medium f-number.
So, why use f-stop instead of actual aperture measurements? Here’s an example. If you’re shooting with a 200mm lens with f/2, your actual aperture measurement would be 100mm. Shoot the same image with a 50mm lens at f/2 and now you need to change your aperture to 25mm. Switch to a 100mm lens and your aperture has to change again to 50mm. Now, I chose f/2 because the math was easy. Imagine you were shooting with f/5.6 and didn’t have a calculator handy! Rather than do a math problem to change the aperture setting for every lens we use, it’s much easier to use f-stops.
Common f-stops on the aperture scale
While your equipment may offer other f-stops than what is listed below, the following is a list of the common f-stops. Each “stop” lets in half as much light as the step above it. However, some modern cameras and lenses also offer half stops, such as f/1.8 and f/3.5.
- f/1.4 (this is a very wide aperture, lets in a lot of light, extremely shallow depth of field)
- f/2 (half as much light as f/1.4, very shallow depth of field)
- f/2.8 (half as much light as f/2.0, small depth of field)
- f/4 (medium aperture, small to moderate depth of field)
- f/5.6 (medium aperture, moderate depth of field)
- f/8 (medium aperture, moderate to large depth of field)
- f/11 (small aperture, large depth of field)
- f/16 (very small aperture, very large depth of field)
- f/22 (very small aperture, very large depth of field, very little light)
- f/32 (the smallest standard aperture, lets in almost no light)
How f-stop affects your image
Aperture affects many aspects of your images—everything from background blur to starbursts and bokeh. But, as a beginner, there are two very important and obvious things that are impacted by your f-stop:
- Exposure: the wider or larger your f-stop, the brighter your image will be;
- Depth of field: the smaller or narrower your f-stop, the more your scene will be in focus;
- And vice versa.
Which f-stop to use and when
Choosing the right f-stop to use is largely subjective, based on experience, preference, and the look you’re trying to achieve. That said, there are some general rules of thumb to help you get started:
- Start with a small aperture (large f-number) on a bright, sunny day;
- Dark skies, night skies, and indoor photography call for wide apertures (indicated by a small f-stop);
- Use a small aperture if you’re using a flash;
- Use a wide aperture (small f-number) if you want a soft, blurry background on your portrait photography;
- If you’re shooting a landscape, start with a small f-stop (a small aperture) so you have a large depth of field.
Like we mentioned above, aperture and f-stops are some of the most important concepts to master when you’re learning to get your camera out of auto. The best way to truly learn is to take your camera out in the field and practice. Capture the same scene at different f-stops and take notice of how it changes both the exposure and the depth of field. It may seem complicated at first, but eventually choosing your f-stop and other exposure settings will become second nature.