As a beginner photographer, you might have heard of such terms as f-stop or f-number and wondered what they mean. Aperture and f-stops can be pretty frustrating to learn at first. Many photographers learning about Aperture for the first time are left with a lot of questions. This article will dive into these in detail and talk about how to use them for your photography. If you need advice on your wedding photography, check out our photography packages and services at Wild Romantic Photography.
Let’s start with a general overview of Aperture and f-stop, and then we’ll dive deeper into these questions.
What is Aperture?
Aperture is one of three camera settings that control relative exposure. The Aperture is the opening in the lens diaphragm, which functions a lot like a human iris. The Aperture is like the pupil of an eye. It opens and closes to let more or less light into the lens. Aperture is measured in f-stops.
What is an F-Stop?
An f-stop (or f-number) is the lens focal length ratio divided by the diameter of the Aperture’s entrance pupil. As such, an f-stop represents the relative Aperture of a lens; it can normalize the aperture setting across different lenses. F-stop and f-number are terms used interchangeably to indicate the aperture setting on a lens.
So Are Aperture and F-Stop the Same Things?
The Aperture is the physical opening of the lens diaphragm. The amount of light that the Aperture allows into the lens is functionally represented by the f-stop, a ratio of the lens focal length and the entrance pupil’s diameter.
The intensity of light that travels through a lens and exposes the camera sensor is dependent on both the length of the lens and the diameter of the opening.
The f-stop considers both by normalizing the diameter of the opening to the lens’s focal length, which results in a relative aperture. This way, the f-stop on one lens allows the same amount of light to hit the sensor as the same f-stop on a different lens. As such, f-stops are relative, not absolute, values that represent a lens’s relative Aperture.
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Why is it Called an F-Stop?
Let’s break down the elements of the notation for an f-stop.
The f stands for focal length, and the number in the denominator is the quotient of the focal length divided by the diameter of the entrance pupil.
Back in the old days, the diaphragm of the lens was adjusted manually by inserting metal plates into the front of a lens (can you imagine?). Each dish was called a “stop” because it stopped light from entering the lens by changing the opening area.
Each “stop” was designed to either double, or half the intensity of light entered through the lens, depending on whether it was removed or added. The word just stuck, and while it makes little sense to us today, it is the terminology used for better or worse.
Is an F-Stop Different Than a Stop of Light?
The word “stop” has another meaning in photography as well. As part of the exposure triangle, aperture, shutter speed, and ISO each use exposure values to increase or decrease relative exposure by equivalent stops of light.
A stop of light is a unit that represents relative exposure. One-stop of light is equivalent to one exposure value (EV). By convention, increasing the relative exposure value by one EV or one-stop of light will double the light’s intensity exposing the sensor. Likewise, decreasing the relative exposure value by one EV will halve the intensity of light. This doubling or halving of the amount of light should sound familiar as it is leftover from the early days when metal stops were inserted into lenses to change exposure.
What is the F-Stop Scale?
The f-stop, which is also known as the f-number, is the lens focal length ratio to the entrance pupil’s diameter. If you did not understand that, don’t worry, because there is a much more straightforward explanation of it for beginners. In plain language, the f-stop is the number that your camera shows you when you change the lens aperture’s size.
You might have seen this on your camera before. On your camera’s LCD screen or viewfinder, the f-stop looks like this: f/2.8, f/4, f/5.6, f/8, f/11, and so on. Sometimes, it will be shown without a slash between f2.8 or with a capital “F” letter in the front like F2.8, which means the same thing as f/2.8. These are just examples of different f-stops, and you might come across much smaller numbers like f/1.2 or much more prominent ones like f/64.
Many lenses have an aperture range where each f-stop is one full stop of light different from the previous or the following f-stop. Here is an example of an f-stop scale with full-stop increments:
f/1.0, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f22, f/32, f/45, f/64
If you have additional f-stop options on your lenses, these likely represent ⅓ or ½ stop increments in addition to the full-stop increments.
Note – many modern camera lenses no longer have an aperture ring, so the Aperture is controlled by the camera body and is viewed via the LCD. On some cameras, you can choose whether full, ⅓ or ½ stops adjust exposure by selecting the increments of exposure control in a menu setting.
Why Are F-Stops Numbered the Way They Are?
There are two reasons why f-stops are numbered the way they are.
The first reason is simple.
As you now know, the f-stop is a fraction. As with all fractions, when the number in the denominator increases, the fraction’s value decreases. For example, a ½ cup of sugar is a lot larger than ⅛ cup of sugar, even though the number 8 is greater than the number 2. Similarly, as f-stop numbers increase, the relative aperture opening decreases. Lower numerical f-stops let in more light than higher numerical f-stops.
The second reason why f-stops are numbered the way they are is a little more complicated.
Let’s recap a few things we know about Aperture first:
- Each f-stop changes the exposure value by one stop of light.
- Each visit of light either doubles or halves the intensity of light hitting the sensor.
- An f-stop is a fraction of the focal length divided by the diameter of the entrance pupil.
Now let’s add the following facts into the mix:
- To achieve a doubling or halving of light intensity, the entrance pupil’s area needs to double or halve.
- The entrance pupil is effectively a circle.
- The area of a circle is A = ?r2. The diameter of a circle is equal to twice the radius.
- Because the area of a circle is proportional to its radius or diameter, you will change the size if you change either the radius or the diameter.
- To double the area of a circle, you multiply the radius or diameter by √2. To halve the size of a process, you divide the radius or diameter by √2.
- So, the f-stop scale appears as a wonky numerical list of numbers because they represent the doubling or halving of the area of a circle, a change that is dependent on the radius (or diameter) changing by a factor of √2 between each f-stop.
Now, we could stop here and tell you to accept this mathematical reality; it will help understand why √2 was the factor needed to have this doubling or halving effect on the entrance pupil area. If you want to know more about the math behind it, then keep reading. If not, remember that as the f-stop numbers increase, the aperture opening decreases. We have the best wedding photographer in Yarra Valley to capture your beautiful moments on your wedding day.
Why Do F-Stops Differ By a Factor of √2?
Unless you geek out on math, you likely don’t readily know why the √2 is the factor used to double or half the area of a circle, and you might find working with square roots a painful experience. The significance of √2 comes from solving the following equation, where A1 is the area of Circle A1 and A2 is the area of Circle2, which is double the area of Circle1.
A2 = 2A1
That’s why the f-stop scale is so odd, thanks to the formula for solving the area of a circle. That wasn’t too bad, was it?
Each f-stop number on the f-stop scale differs from the previous and the following f-stop by a factor of √2, resulting in the doubling or halving of the entrance pupil area, which changes the relative exposure by one stop of light (one exposure value) in either direction.
Why Aperture is Important
As we have previously defined, an Aperture is a hole in your camera’s lens that lets light pass through. It’s not a particularly complicated topic, but it helps to have a good mental concept of aperture blades in the first place.
Yes, aperture blades, which are also known as the diaphragm in optics. Take a look inside your camera lens. If you shine a light at the proper angle, you’ll see something that looks like this:
These blades form a small hole, almost circular — your aperture. They also can open and close, changing the size of the Aperture.
That is an important concept! Often, you’ll hear other photographers talking about large versus small apertures. They will tell you to “stop down” (close) or “open up” (widen) the aperture blades for a particular photo. As you would expect, there are differences between photos taken with a large aperture versus photos taken with a small gap. Aperture size directly impacts a photograph’s brightness, with larger cracks letting in more light into the camera than smaller ones. However, that isn’t the only thing that Aperture affects.
The other more critical impact is the depth of field – the amount of your photo appears to be sharp from front to back.
Depth of Field at Different Aperture Settings
Adjusting your Aperture is one of the best tools you have to capture the right images. You can change it by entering your camera’s aperture-priority mode or manual mode, both of which give you free rein to pick whatever aperture you like.
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Why is Aperture Written as an f-number?
Why is your aperture written like that? What does something like “f/8” even mean? This is one of the most critical parts of Aperture: it’s written as a fraction.
You can think of an aperture of f/8 as the fraction 1/8 (one-eighth). A gap of f/2 is equivalent to 1/2 (one-half). A gap of f/16 is 1/16 (one-sixteenth). And so on. Hopefully, you know how fractions work. 1/2 cup of sugar is much more than 1/16 cup of sugar. A 1/4 pound burger is more significant than a 1/10 pound slider. By that same logic, an aperture of f/2 is much larger than an aperture of f/16. If you ever read an article online that ignores this simple fact, you’ll be very confused.
Pop quiz: Which Aperture is larger — f/8 or f/22?
You already know the answer to this question because Aperture is a fraction. 1/8 is more significant than 1/22. So, f/8 is the larger Aperture. If someone tells you to use a large aperture, they’re recommending an f-stop like f/1.4, f/2, or f/2.8. If someone tells you to use a small gap, they’re recommending an f-stop like f/8, f/11, or f/16.
What Does the “f” Stand For?
Many photographers ask me an interesting question: What does the “f” stand for in f-stop or the name of aperture (like f/8)?
Quite simply, the “f” stands for “focal length.” When you substitute focal length into the fraction, you’re solving the aperture blades’ diameter in your lens. (Or, more accurately, the diameter that the edges appear to be when you look through the front of the lens).
For example, say that you have an 80-200mm f/2.8 lens fully zoomed out to 80mm. If your f-stop is set to f/4, the diameter of the aperture blades in your lens will look exactly 20 millimetres across (80mm / 4), whereas at f/16, the diameter will be reduced to mere 5 millimetres (80mm / 16). This is an excellent concept. It also makes it easy to visualize why an aperture of f/4 would be more significant than an aperture of f/16.
Which F-Stop Values Can You Set?
Unfortunately, you can’t just set an f-stop value that you want. At some point, the aperture blades in your lens won’t be able to close any smaller, or they won’t be able to open any wider. Typically, the “maximum” Aperture of a lens, often referred to as “wide-open” Aperture, will be something like f/1.4, f/1.8, f/2, f/2.8, f/3.5, f/4, or f/5.6.
A lot of photographers care about the maximum Aperture that their lenses offer. Sometimes, they’ll pay hundreds of extra dollars to buy a lens with a maximum aperture of f/2.8 rather than f/4, or f/1.4 rather than f/1.8.
Why is a large maximum aperture in a lens so important? Because a lens with a larger maximum aperture lets more light into the camera. For example, a lens with a maximum aperture of f/2.8 lets in twice as much light when compared to a lens with a maximum aperture of f/4.0. This difference could be a big deal when shooting in low-light conditions.
Since people care so much about maximum Aperture, camera manufacturers decided to include that number in the lens’s name. For example, one of my favourite lenses is the Nikon 20mm f/1.8G. The largest Aperture it offers is f/1.8.
Photographers generally don’t care as much about the most minor or “minimum” Aperture that the lens allows, which is why manufacturers don’t put that information in the name of the lens. However, if it matters to you, you will always be able to find this specification on the manufacturer’s website. A lens’s smallest Aperture is typically something like f/16, f/22, or f/32. We have an exclusive range of wedding photography Mornington Peninsula services. Check them out here.
F-Stop and Depth of Field
Along with the amount of light a lens aperture allows, it has one other massive effect on your photos – depth of field.
Depth of Field Comparison f4 vs. f32
This is very interesting! As you can see, in the f/4 photo, only a thin slice of the lizard’s head appears sharp. The background of the image is very blurry. This is known as depth of field.
You can think of the depth of field as a glass windowpane that intersects with your subject. Any part of your photo that intersects with the window glass will be sharp—the thickness of the glass changes depending upon your Aperture. At something like f/4, the glass is relatively thin. At something like f/32, the glass is very thick. The field’s depth falls off gradually rather than dropping sharply, so the window glass analogy is a simplification.
This is why portrait photographers love f-stops like f/1.4, f/2, or f/2.8. They give you a pleasant “shallow focus” effect, where only a thin slice of your subject is sharp (such as your subject’s eyes).
The most popular genre of photography is cat photography! If you want a shallow focus effect, set a large aperture like f/1.4. That’s what I used here to capture this cat’s eyes as sharp as possible while rendering the background extremely out of focus. (This also works for portraits or any other subject.)
On the flip side, you should be able to see why landscape photographers prefer using f-stops like f/8, f/11, or f/16. If you want your entire photo sharp out to the horizon, this is what you should use.
Here’s the aperture scale. Each step-down lets in half as much light:
- f/1.4 (massive opening of your aperture blades, lets in a lot of light)
- f/2.0 (lets in half as much light as f/1.4)
- f/2.8 (lets in half as much light as f/2.0)
- f/4.0 (etc.)
- f/32.0 (tiny Aperture, lets in almost no light)
These are the central aperture “stops,” but most cameras and lenses today let you set some values in between, such as f/1.8 or f/3.5.
Usually, the sharpest f-stop on a lens will occur somewhere in the middle of this range — f/4, f/5.6, or f/8. However, sharpness isn’t as important as things like depth of field, so don’t be afraid to set other values when you need them. There’s a reason why your lens has so many possible aperture settings.
Other Effects of F-Stop
The second page of our aperture article dives into every single effect of Aperture in your photos. It includes things like diffraction, sun stars, lens aberrations, and so on. However, as necessary as all that is, it’s not what you need to know – especially at first.
Instead, know that the two biggest reasons to adjust your Aperture are to change brightness (exposure) and depth of field. Learn those first. They have the most apparent impact on your images, and you can always read about the more minor effects later.
Aperture vs. F-Stop
When it comes to photography, there are many jargons used that might seem overwhelming to a beginner. Aperture and F-stop are among these two terms. What’s more confusing is that many people use these two terms interchangeably. Technically, Aperture is the size of the hole that lets light in. In cameras, this is the diameter to which your diaphragm opens up to. A small diameter diaphragm opening lets little light in, and a bigger would correspondingly let more light in. In comparison, the F-stop is simply a scale that correlates the Aperture to the lens’s focal length. A longer lens can have a bigger aperture, while a shorter lens can have a smaller aperture, yet they would be at the same F-stop.
The main reason why F-stop is prevalent in photography is the scaling. It is a fact that every time you increase one step on the F-stop, you are halving the amount of light that enters the sensor. Aperture sizes are not scaled in the same manner, so you have no idea how much light is entering your sensor.
In actual photography, the F-stop is commonly used rather than the actual aperture of the lens. The amount of light is the most critical aspect in photography as too little results in an underexposed photo while too many products in an overexposed image. In cases where you want to limit or expand the subject’s focus by adjusting the size of the Aperture, choosing a higher or lower F-stop would achieve the same result. Correct exposure is still performed by adjusting the shutter speed. A faster shutter speed compensates for a bigger aperture, while a slower shutter speed compensates for a smaller gap. However, the latter is susceptible to blurring, especially when the camera is not mounted in a fixed position.
These two terms are used interchangeably, and there is nothing wrong with that; most of the time, they refer to the same thing. Just keep in mind that these two have an inverse relationship. As the F-stop value goes up, the aperture size goes down.
Hopefully, you now have a good sense of the f-stop and the ways it affects your photos.
Of course, putting everything into practice is another matter. Even if this entire article makes sense, for now, you’ll still need to take hundreds of photos in the field, if not thousands, before these concepts become entirely intuitive. If you’d like to work with professional photographers for your wedding, book with us at Wild Romantic Photography.
Luckily, you have the building blocks. Aperture and f-stop aren’t complicated topics, but they can seem counterintuitive for photographers who are just starting. Hopefully, this article clarified some of the confusion, and you now have a better understanding of the fundamentals of Aperture.