- What Is the F-Stop on a Camera? Before we would jump right into it, it’s essential to understand how the aperture works. To keep it short, the aperture blades, also known as a diaphragm in your lens work just like the pupil of the human eye.
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One of the first steps to learning photography is understanding the exposure triangle and how to manipulate exposure in your images. Parts of the exposure triangle are complex, while others are straightforward.
For example, it takes a little while to learn recommended shutter speeds, but it’s easy to understand how different shutter speeds affect both exposure and motion blur. Similarly, while the technical aspects of ISO are somewhat obscure, the tradeoff between brighter/noisier and darker/cleaner images is fairly clear (e.g. use the lowest possible ISO that will give you a good exposure).
Aperture and f-stops are concepts that are more difficult to grasp. When you start talking about f-stops, you run into some seemingly paradoxical concepts between large and small apertures, large and small f-stops, and how they affect your overall image. To help you better understand f-stops and aperture, take a look at our f-stop chart.
F-Stop Chart
Before we get too deep into what f-stops are and how to pick which one to use, let’s take a quick look at the major f-stop values. This f-stop chart shows how they influence the size of the aperture in your lens, the overall exposure and depth of field, and common uses for f-stops.
What is Aperture?
It’s helpful to review what aperture is to help you better understand f-stops.
Practically every lens has an iris consisting of multiple blades arranged in a ring. These blades form a hole through which light can pass through before hitting the camera’s sensor or film. This hole is called the aperture. The iris’s blades can move in order to make the aperture larger or smaller.
Because all the light that hits the sensor must pass through this hole, it has an obvious impact on the exposure of the image. A larger aperture lets in more light resulting in a brighter picture.
In addition, the aperture is one of the major factors (along with focal length and distance to the subject) in determining an image’s depth of field. If all other factors are the same, a larger aperture will have a shallower depth of field while a smaller aperture will have a wider depth of field.
What is F-Stop?
An f-stop is a measurement of the aperture opening based off of the size and type of your lens.
Mathematically, f-stops are calculated as the ratio of the focal length of the camera divided by the diameter of the aperture.
What Is A F-stop
For example, a 100mm lens with an aperture diameter of 50mm has an f-ratio of ½, while the same lens with an aperture diameter of 25mm has an f-ratio of ¼, and an aperture diameter of 10mm has an f-ratio of 1/10. When looking at your camera or lens, the f-stops are simply these ratios rewritten with an f in the top spot of the fraction (f/2, f/4, and f/10 respectively for the above examples).
This introduces the most confusing part of f-stops. As these examples show, the larger the number in the f-stop label, the smaller the actual diameter of the aperture.
While you don’t need to necessarily remember the math of how an f-stop is calculated, it can be helpful to remember the fractional origin of the number. If you need a larger aperture for a brighter exposure or a shallower depth of field, the number in the f-stop will be smaller, while smaller apertures will have larger f-stop numbers.
A lens will usually be stamped with the lowest f-stop it can go (typically the lower the available f-stop the better quality/more expensive the lens). A zoom lens may have a variable aperture and f-stop. If the lens is zoomed out, it will be able to shoot at the lowest f-stop. If the lens is zoomed in, it may only be able to shoot at a higher f-stop. For example, the Canon RF 100-500mm f/4.5-7.1L IS has a maximum aperture of f/4.5 when shooting at 100mm while only a max aperture of f/7.1 when shooting at 500mm. Compare this to the Canon RF 70-200mm f/2.8L IS, which can shoot at f/2.8 no matter where you are in the zoom range.
How Do You Read an F-stop?
At this point, you might be worried that you’ll have to remember calculations and complex ratios. The good news is that once you memorize the major f-stops, it’ll be smooth sailing.
The main f-stops are f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, and f/16. Each of these is what’s called a stop, and depending on your camera you might be able to change a setting to adjust exposure in either ⅓ stops (e.g., f/5.6, f/6.3, f/7.1, f/8) or ½ stops (e.g., f/5.6, f/6.7, f/8).
When you talk about stops in relation to exposure, you are saying that something is twice or half as bright (½ and ⅓ stops are, as you might expect, simply dividing a full stop into two or three segments for fine tuning your exposure settings).
With shutter speed, increasing from 1/50sec to 1/100sec cuts the time the shutter is open in half, letting half as much light hit the sensor, and cutting the brightness in half. ISO values were set and standardized such that doubling or halving the numbers also doubles or halves the brightness of the exposure. Flashes are often set in stops to make adjusting the brightness consistent with camera settings. With aperture, the f/stop sequence designates the stops.
Once you learn the sequence of f-stops, it becomes easy to quickly adjust your aperture, shutter speed, and ISO together to dial in your desired exposure. Adjusting one setting by a full stop one way can be countered by changing another a full stop the opposite direction (or both other settings by ½ stop each). This is vital if you want to ensure that you freeze (or blur) motion or change the depth of field while still keeping the overall exposure that you have chosen.
In fact, you can even take a shortcut and just count how many times you click one of the settings and completely forget what exact numbers you are using. Turning your shutter speed dial three clicks brighter? Just turn your aperture dial three clicks darker to keep the same exposure.
What Should My F-stop Be Set At?
If you’re just starting to take control of your camera’s settings and learning how to use manual mode you might be thinking, “This is all interesting, but just tell me what my f-stop should be set at.” As with so many things, it depends on what you’re shooting.
A popular style of portraiture is to have a razor-thin depth of field that blurs everything in the background. To achieve this, you need extremely low f-stops. Many shoot at f-stops of f/2 or below. However, some lenses cannot achieve apertures that wide. Your depth of field may also often become so thin that you can’t properly focus on the eye, which is critical with these shots. Depending on the situation, you might be able to stop down to f/2.8 or even f/4 and get similarly pleasing results.
On the other hand, if you want a wide depth of field with a lot of the scene in focus. You need to stop down your aperture significantly, but be aware that too small of an aperture introduces a type of distortion called diffraction that can make your images less sharp. Most lenses have a sweet spot somewhere around f/8 or f/11 that maximizes depth of field without introducing much diffraction. But if you’re shooting subjects like landscapes or macro, you might decide the tradeoff is worth it. Spend some time experimenting to determine what f-stops work best with your shooting style.
Learning how to choose the ideal f-stop is a key step in taking control of your images. Not every lens offers the same range of f-stops. Your style of photography will help inform the range you need. Not every style of photography needs the widest possible range of apertures. If you’re still trying to figure out the best f-stops to choose for your own pictures, consider renting some lenses with specific aperture options so you can try them out for yourself.
Tags: Best Camera Settings, Cameras for BeginnersLast modified: December 13, 2020So what exactly is an f-stop? Well, to put it in the very simplest terms, it is the opening that lets light into your camera. And so the numbers on the f-stop relate to the size of the opening that is letting light into your camera. F-stops are measured by a scale, and this is known as the f-stop scale. If you are not familiar with a camera, the f-stop numbers can be very confusing, as they do not seem to make any sense. F-stops are actually a measurement of the diameter of the aperture. Logically, they should be expressed as a fraction and this number would tell you the diameter, in millimeters, as a fraction of the actual focal length of the lens. So if you had a zoom set at 40mm with an aperture of f/8, the diameter of the aperture opening is 5mm (40 divided by 8).
photo by Adrià Ariste Santacreu
Adding to this confusion, the numbers that correspond to different f-stops seem backwards, because an aperture of f/8 is actually smaller than an aperture of f/4. So, the larger the number, the smaller the opening. And the smaller the number, the larger the opening.
And then you get into the fact that most f-stop numbers are not a full number. They are an f/5.6, or an f/19, or an f/6.3, or an f/1.4. If you are not familiar with f-stops and aperture openings, none of this makes any sense. These numbers depict half stops and third stops, as well as full f-stops.
The typical range for f-stops on a camera, progressing from a wide setting to a small setting is f/4, f/5.6, f/8, f/11, and f/16. Some lenses will have a wider range and may offer half stops and/or third stops.
Another funny thing about f-stops, is if you halve the number of the f-stop, the aperture lets in a quarter amount of light, because it is it two stop decrease. If you are thinking about it logically, you would naturally assume that if you took and halved your f-stop that you would be letting in half the light. But that is not true because with each f-stop decrease you are halving the amount of light, therefore with two f-stops, you would only have one quarter of the light.
If you take your f-stop scale, and add your half stops, the scale is f/4, f/4.8, and f/5.6. If you then do your third stop range. It would go f/4, f/4.5, f/4.8 (for your half), f/5 and f/5.6.
The key thing to remember about f-stops is that it is a measure of the amount of light that is being let in through your lens. You can think of it as having a paper towel roll, and looking through the roll at the light. If you took a piece of tinfoil and put it over the end of the paper towel roll and poked a pinhole in it, you would have a high f-stop or small aperture opening. The bigger you made the hole, the smaller your f-stop number would become and the more light you would be letting in. Using your aperture control with your shutter control on your camera will give you the proper exposure. The best way to figure out what is happening with the different settings, is just to play with it. Especially if you have a digital camera, you can just delete whatever doesn’t turn out well.
Don’t worry if you don’t know what all the controls on your camera mean. You can learn as little or as much as you want. After all, you can always just set it on auto and your camera will take the picture for you, and chances are it will turn out great. The manual controls are for those shots your camera has a hard time taking, or just for some creative control. Maybe you don’t want your shot to look like reality. I post information that you may find helpful in learning how to use your camera. And if it is time for you to buy a new camera, I can help with that too.
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You mean 40/8 right? Not 40/40.
1) I second David A.
2) Also, a comment….I believe you contradict yourself; if you follow the logic of taking the focal length divided by the effective aperture to get the f-stop, then it’s not confusing at all that a larger aperture makes a smaller f-stop. That’s the foundation of division!
i dont get it.
Your ‘errors’ have already be pointed out by others, but I believe that “f-Stops” must have been invented by Brits, as they seem to complicate everything and make everything as awkward as possible. Thus the smaller the F.#, the larger the Aperture. I rest my case!
Right…not all simple and logical like our systems huh?
Well i have to say that this article left me way more confused about f-stops than before i read it.
I have aPanasonic Lumix FZ70 and the f-stop goes to f8 only- yet I noticed on other people’s cameras it goes as hight f16 – does it matter?
Thanks Irene
Hi every body,
I have a 6 inch catadioptric telescope which I know is 150/1400. Now I know that the 150 equates to six inches, thus the diameter of my main mirror and the focal length is 1400mm. My question is:
what is 1400mm expressed as an f stop?If anyone could give me the answer together with the formula to work it out, I would be most grateful.
I thought it was explained very well, especially after trying to understand what others explained.
> Another funny thing about f-stops, is if you halve the number of the f-stop, the aperture lets in a quarter amount of light, because it is it two stop decrease.
This makes no sense at all.
If I halve the number of the f-stop… ok let’s start at 4. I halve it to 2 and the aperture lets in a quarter of the amount of light? Well clearly not, since 2 is a much larger aperture than 4 and will allow in MORE light, not less and certainly not a quarter of it.
> But that is not true because with each f-stop decrease you are halving the amount of light, therefore with two f-stops, you would only have one quarter of the light.
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