Aperture is one of the most important settings in photography – it affects the depth of field and the exposure of a photograph. When it comes to understanding the way Aperture works though, there are plenty of factors to consider. While aperture itself might seem simple, one also needs to consider F-Stops, Focal Length, Focus Distance and something aptly named the Confusion Circle to fully understand it! There’s also the matter of exposing correctly, and the way aperture interacts with other elements of the Exposure Triangle. All of these elements combine to create Depth of Focus and Bokeh, a much sort after blurring effect in modern photography trends.
Thankfully, learning to use aperture is nowhere near as complicated as the theory behind it! Like many things in life, all it takes is practice makes perfect. To give you a kickstart though, we’ve put together some simple guides to Depth of Field. Depth of Field doesn’t need to be difficult! That’s true whether you want to try your hand at Product Photography, Portrait Photographer, Fashion Photographer or a Landscape Photographer.
So dive on in to our Complete Camera Aperture Guide, and take your photography to the next level!
WHAT IS APERTURE IN PHOTOGRAPHY
If you look into any camera lens, you’ll see a hole in the middle where light travels through. This is the aperture, constructed with a series of overlapping blades that work together to create a larger or smaller hole. It works somewhat like the pupil of the human eye. If you look at your eyes in a mirror with the lights turned on, you’ll notice your pupils are quite small. If you turn the lights off, you’ll notice your pupils widen. This is to let more or less light in so that the brain can successfully convert what we see into an image. In photography, aperture works the same way, except aperture affects more than just the amount of light that the lens lets in.
Image by WClarke via commons.wikimedia.org
THE EXPOSURE TRIANGLE
Before we get to that though, it would be impossible to talk about aperture without discussing exposure. The term exposure comes from the very beginning of photography’s history. The earliest photographs were taken on light-sensitive plates of metal, glass and paper. To make the photo, the plate had to be exposed to light for a specific amount of time, hence ‘exposure’. The same principle lives on in digital photography, it’s just that the light is exposed to a sensor.
In order to correctly expose a photograph, a photographer needs to consider the Exposure Triangle. The Exposure Triangle refers to the three settings that work together to control the amount of light a photograph receives – Aperture, Shutter Speed and ISO.
BUT FIRST, WHAT’S A STOP?
Before going into the details of the Exposure Triangle, it’s important to understand what it means to ‘stop up’ or ‘stop down’. These are phrases that photographers use regularly, and are key to understanding Exposure. A stop is simply a way to refer to doubling or halving the amount of light that creates an exposure. Where stopping up means doubling the light, stopping down refers to halving the light. If a photographer finds themselves in a low-light situation, they’ll need to use settings that allow more light in. The opposite goes for situations with abundant lighting. Learning the different ways to stop down and stop up is key to understanding photography, and it’s all done through the Aperture, Shutter Speed and ISO.
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THE EXPOSURE TRIANGLE: APERTURE
As we said before, aperture works like the pupil of the human eye to let light through the lens. The more open the aperture ring, the more light a lens lets in. Of course, the desired amount of light will depend on the situation, as well as the Exposure Triangle. It’s impossible to declare that one particular aperture setting, or F-stop, will always provide the best results!
APERTURE: WHAT IS AN F STOP?
An F-stop is simply the number used to express the aperture setting. If you have a camera handy, check the barrel of your lens. It’s likely you’ll see a series of numbers ranging anywhere from 0.95 to 22. These are F numbers. Or if you’re using a digital camera, you can check the settings on your screen. In this case, the F-stop might be written like this: f/2, f/3.2, f/5.6, f/9, f/11, f/16, f/22.
A confusing part of aperture can be the way photographers refer to it. A photographer might say that they need to ‘stop down’ and then change the aperture from f/2 to f/4. Or, they might say they need to ‘shoot wider’ and change their F-stop from f/4 to f/2. Why is it that a seemingly smaller number creates a larger aperture opening and vice versa?
What is the significance of F-Numbers?
This is because F numbers are actually fractions! This means that you can effectively think of f/2 as a half and f/4 as a quarter. For those who are little rusty on maths, all you need to do is imagine a cake. If you eat a quarter of a cake (1/4) you’re eating more than if you eat an eighth of a cake (1/8). That means that a large or wide aperture will be in the range of f/1.4, f1.8 or f/2. On the other hand, a small or closed aperture will be something like f/16 or f/22.
The next question I’m sure you have is, ‘but what is the F-stop a fraction of?’ Thankfully, the answer is quite simple. The f-stop is a fraction of the focal length of a lens. So if you have a 100mm lens set to f/2, then your aperture is open 50% of 100mm, being 50mm.
The maths doesn’t end there though! F-numbers seem like a pretty odd sequence of numbers, but actually they’re a geometric sequence. Each number is the next square root of 2. This is because every time the F-number moves either up or down, the aperture diameter is either doubled or halved. If you think back to Stops of Light, you’ll now understand that to moving 1 stop up or 1 stop down using aperture is easy. A stop down might be moving from f/2 to f/2.8. A stop up could be moving from f/8 to f/5.6.
If you happen to have an analogue lens with manual aperture controls available, try experimenting. Hold the lens up to the light and watch the aperture hole change in size as you move the aperture ring!
Photo by Markus Spiske on Unsplash
How is f/0.95 possible?
You might have noticed that the initial F-numbers we gave ranged between 0.95 and 22. Given that aperture is a fraction of the focal length, shouldn’t an aperture of f/0.95 be impossible! It’s not, it just means the lens has an aperture opening that’s wider than the lens’s focal length. Understandably, a photo taken using an F-stop of f/0.95 would have an exceptionally narrow depth of field.
Finally, while the F-numbers themselves can seem a little complicated, the meaning of the “F” itself is easy. It simply stands for ‘focal length’.
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THE EXPOSURE TRIANGLE: SHUTTER SPEED
Where aperture impacts exposure because it determines how much light is let in to the lens, shutter speed is important because it determines how long that light has to pass through the lens. Thankfully, shutter speed is also a lot easier to understand than aperture. A fast shutter speed, measured in fractions of a second, allows less time for light to pass through the lens. The result will be a lower exposure than that of a long or slow shutter speed. This is because a slow shutter speed means the shutter stays open for longer, allowing more light to pass through.
Moving a stop up or a stop down using Shutter Speed is simple. To stop up, you simply need to double the exposure time. For example, you could move from a shutter speed of 1/500 to 1/1000. To stop down, you need to halve the exposure time, moving from say 1/250 to 1/125.
Shutter speed doesn’t just affect the exposure though, it also effects the movement of a photograph. For the time that the shutter is open, it is effectively capturing everything that passes in front of it. This means if something moves, that movement might be captured in the photograph creating a blurred image. In sports photography, for example, this would not be ideal. As such, sports photographers would rarely user a shutter speed that’s slower than 1/1000th of a second. A landscape photographer is more likely to use a long shutter speed, moving up to multiple seconds. This is because capturing movement of water, for example, can have a very beautiful effect. Of course, to capture a sharp image at a slow shutter speed, a tripod is necessary to avoid any movement or shaking from the photographer’s hands!
THE EXPOSURE TRIANGLE: ISO
The final element of the Exposure Triangle is ISO. ISO is an old term from the days of film photography that refers more or less to the sensor’s light sensitivity. Of course, technically it’s far more complicated, but we don’t need to get into that! Put simply, a higher ISO means a higher light sensitivity. A low ISO on the other hand means that a sensor will need lots of light to make an exposure. To give an idea, ISO 100 would be used when taking photographs outside on a bright, sunny day. ISO 3200 on the other hand might be used in a dark bar with very little ambient lighting.
Like shutter speed, the ISO ‘stop’ scale is very easy to understand. Doubling the ISO equals to moving 1 stop up. Instead, halving the ISO is equal to moving 1 stop down.
WHAT IS DEPTH OF FIELD?
A common question asked of photographers is ‘how do you get that blurry background effect?’ The short answer is through playing with Aperture in this case, specifically with wide open aperture. The effect being referred to is technically called a narrow Depth of Field.
Depth of field is the distance between the closest and farthest objects in a photo that are sharply focussed. Technically, a camera can only focus sharply on one point. Whether the objects around that point will be in focus or not depends on the photographer’s Aperture setting.
Let’s say, for example, I decide to take a photo of a tree. We’ll get more into the details later, but if in this photo you can only see one leaf and the rest of the tree is blurry, the photo has a Narrow Depth of Field. This is achieved by using a low F-stop, such as f/1.4. Depending on the lens and the lighting of a photo with Narrow Depth of Field, you might notice aesthetically pleasing circular blurring in the background. This is called ‘bokeh’. On the other hand, if the entire tree is sharply focussed, and perhaps even its surrounding environment, the photo has a Large Depth of Field. This is achieved by using a high F stop like f/16.
LENSES, APERTURE AND DEPTH OF FIELD
If you have a few different lenses, you might have noticed that the quality of the Depth of Field changes with each lens. This is because Depth of Field is not just a function of aperture. Instead, aperture works together with a lens’s focal length, the amount of space between a camera and its subject, and the Circle of Confusion to create Depth of Field. This means to fully understand Depth of Field, a basic understanding of the way a lens works is required.
Image by Vitaly Baranov via commons.wikimedia.org
LENSES: THE IMPORTANCE OF FOCUS
Effectively, a lens is a tool that rearranges light in order to capture an image. The light passes through the lens glass at a range of angles and curves, before it is rearranged to recreate the image in front of it. The reason the light arrives at a range of angles and curves is because the subject of a photograph is almost always larger than the surface of the lens being used. Of course, if the light is being bent through the lens to fit the whole scene in, it’s important that light arrives at the right place!
It is this bending and refracting of light that creates Depth of Field. If the rearranged light of a specific object comes together again before it reaches the sensor, it will be blurry. The same is true if the light meets again after the sensor. The light reflecting off of a specific point in the photo needs to come back together again where the sensor is to be sharply focussed.
The focal plane, or what one can see through a lens, of a camera is razor thin. Without aperture and focus, a photographer would have to constantly move their camera to put their desired subject in focus. Thankfully, your lens moves for you instead. Just try moving a mechanical focus ring! As the lens barrel moves in and out, it’s changing the distance between the lens glass and its sensor, changing the point where the light converges.
WHAT CONTROLS DEPTH OF FIELD: FOCUS
Now that you can (hopefully) picture light converging into a lens, the principles of Depth of Field should be a little clearer. Depending on where the light rays converge, different parts of the photo will either be in focus or out of focus.
Where the photo is in focus, say a person’s nose, the light refracting from their nose has converged at a single point either at the sensor or very close to the sensor. Let’s say that in the same photo, the subject’s hair is out of focus. This means the light reflecting from their hair hasn’t unified by the time it reaches the sensor, instead, it is still a larger group of light rays travelling together. As such, the blurry hair will take up more space than the single point of the nose, usually in the form of a blurry circle. If the nose is in focus, and the hair is not, the distance between the sharply focussed and not-focussed objects of a photo is quite short, making it a Narrow Depth of Field. But still, different lenses will capture this in different ways.
WHAT CONTROLS DEPTH OF FIELD: CIRCLE OF CONFUSION
Unfortunately, the Circle of Confusion isn’t referring to a photographer’s confusion as they attempt to learn about Aperture and Depth of Field! We know – it’s complicated! Instead, the Circle of Confusion, or Focus Spot, refers to the largest point of light that still looks in focus in an image.
Let us explain. Before, we said that a camera can only focus sharply on one point. So how is it that a photo of a mountain can seem to be sharp at every point? Well, this depends on the Circle of Confusion and the convergence of light we talked about under the Focus section. While the exact focus point of an image will be the point where the rays of light meet perfectly at the sensor, points of light that arrive relatively close to the sensor can still seem in focus. Although technically slightly blurry, a human eye won’t pick up on that. The Circle of Confusion then is the largest point of light that still appears to be in focus.
If the Circle of Confusion is still confusing to you, we’d recommend checking out B&H Explora’s article on the topic. After all, their informative blog was one of the reasons that they were our number one choice for Where to Buy Photography Gear Online!
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WHAT CONTROLS DEPTH OF FIELD: APERTURE
Given that the way a light falls through a lens is responsible for the focus and hence the Depth of Field, it only makes sense that aperture and depth of field are so closely linked. Think about it! If the light only has a tiny gap through which to pass to reach the sensor, say f/22, it will surely change the way the light falls onto the sensor than if the aperture was set to f/2. As we said before, the higher the F-stop, the narrower the Depth of Field. The lower the F-stop, the wider the Depth of Field. But why?
Large Aperture
You know that a large aperture means that the aperture diaphragm is wide open. This means there is a greater space through which the light can pass, and so the light would need to bend significantly to reach the single point of the sensor. As we know from learning about focus, any light that converges before or after the sensor will be out of focus, creating blurry spots. Moreover, the light will be travelling at a wider angle than a photo taken with a small aperture, because of the space allowed. These wider light rays will create larger blurry spots. This is why a large aperture likely will create a photograph with a Narrow Depth of Field. Also, with a Narrow Depth of Field there’s more chance of achieving beautiful ‘bokeh’, the big blurry spots that might appear in ‘unfocussed’ areas of a photo.
Small Aperture
On the other hand, a small aperture means that the aperture diaphragm will be very small. As such, the light has less room for movement and it is much more likely it will reach the sensor at the point it converges. More importantly though, because the light will bend less when it enters the lens, the blurry spots it forms will be smaller. Of course, smaller blurry spots are more likely to fall within the range of acceptable focus, and a Large Depth of Field is achieved.
So, if you’d like photos with beautiful, soft Bokeh and a Narrow Depth of Field, you should use a large aperture. If you prefer photos with a Large Depth of Field, try a small aperture.
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WHAT CONTROLS DEPTH OF FIELD: FOCAL LENGTH
Put super simply, focal length is responsible for how ‘zoomed in’ a photo will be. It refers to the optical distance and is measured based on the angle of a lens’s view. Commonly used everyday lens sizes range from around 24mm to 105mm. The higher the number, the narrower the view and the higher the magnification.
For example, let’s say you are taking photos at a wedding ceremony. You are standing behind the guests and you want to take a photo of the couple. If you take a photo with a 24mm lens, the couple will likely be quite small, and the guests will be included in the shot. If you take a photo with a 105mm lens, the photo might include just the upper bodies and faces of the couple.
In more technical terms, the focal length is the distance between the point of light convergence in a lens to the camera’s sensor or film. This not only affects the amount your camera can ‘fit in’ to a photo, but also the Depth of Field. The length of a lens, much like aperture, changes the way light refracts through the lens, affecting Depth of Field.
Short Focal Length vs. Long Focal Length
Specifically, a lens with a shorter focal length, for example a 24mm, will need to bend light at a sharper angle. Because of this, the light tends to converge closer to the sensor or film. Similar to the effect of using a high aperture, this creates a Large Depth of Focus. On the other hand, light falling through a lens with a long focal length, for example a 105mm, will bend less. This means the light is more likely to converge further away from the sensor, creating larger blurry spots and a Narrow Depth of Focus.
So, if you’d like photos with a Bokeh and a Narrow Depth of Field, you should use a lens with a longer focal length. But if you prefer photos with a Large Depth of Field, you should use a Shorter Lens.
WHAT CONTROLS DEPTH OF FIELD: FOCUS DISTANCE
The final factor that affects Depth of Focus is the Focus Distance. Also known as Subject-to-Lens Distance, this is simply the distance from the lens to the subject you are focussing on. Once again, this is where having an old analogue style lens comes in handy, as the barrel was almost always marked with the distances, which always ended in ¥. Unfortunately, newer lenses often don’t have these markings.
In terms of Depth of Field, by moving the lens closer to the subject, a photographer will achieve a Narrow Depth of Field. This is because the light rays would need to bend more to intersect near the sensor, creating larger blurry circles. On the other hand, if the subject is further away from the lens, the light rays will be narrower. This means they will need to bend less to converge near the sensor, creating smaller blurry spots and a larger Depth of Field.
WHAT CONTROLS DEPTH OF FIELD: HYPERFOCAL DISTANCE
Many photographers can get away without even knowing what Hyperfocal Distance is! If you’re interested in Depth of Field though, it’s an important tool. Hyperfocal Distance is a way to maximise Depth of Field by adjusting the F-stop and Focus Distance. While it can be applied to any lens, it’s mostly used in conjunction with wide-angled lenses. Landscape photographers especially use Hyperfocal Distance to maximise sharpness throughout a scene.
An Example of Hyperfocal Distance
Let’s say you are trying to take a photo of a vast landscape, perhaps some desert sand dunes. The automatic tendency when photographing such a landscape is to move the focus ring to ¥ with an aperture of f/22. This way seems like the best way to achieve focus across the image. However, it’s likely that everything that falls within the first few feet of the scene won’t be focussed.
Now let’s say you focus on something a couple of feet in front of the lens, say a small flower you’ve found. In this case, it’s likely the dunes in the distance will be blurry. This is where Hyperfocal Distance comes in. To ensure everything will be in focus, set your lens to a distance that is halfway between the furthest and closest focus points of your scene. It may seem blurry when looking through the lens, but the end result will be a focussed image!
Of course, there’s no single winning formula to determine Hyperfocal Distance, but luckily, these days there is an app for everything! Just search your phone’s app store for ‘Depth of Focus’ and choose the one you like the most!
DEPTH OF FIELD: A BASIC HOW-TO GUIDE
All of this information can definitely cause information overload. But at the end of the day, if all you want to know is how to control your depth of field, then it’s quite simple.
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SHALLOW DEPTH OF FIELD
To achieve a shallow depth of field, you should use:
- A long lens
- Shoot with the aperture ‘wide open’, or at a high F-stop
- Maintain a short Focus Distance
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DEEP DEPTH OF FIELD
To achieve a deep depth of field, you should use:
- A short lens
- Shoot with the aperture closed, or at a low F-stop
- Maintain a long Focus Distance
WHAT’S THE BEST DEPTH OF FIELD FOR EACH PHOTOGRAPHY TYPE
Of course, the first step to achieving the right Depth of Field for your photographs is having the right equipment. Key to this is having a camera that allows you to change all the settings manually. Using your camera and practicing is always the best way to learn the right settings for your style of photography. It never hurts to have a few handy tips to start off with though! Here’s some examples of settings you can use to achieve the Best Depth of Field for Each Photography Type.
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PORTRAIT PHOTOGRPAHY
Portrait photographs generally call for a shallow Depth of Field. This way, the person being photographed will stand out against the blurred background. Generally, standard portrait lenses range from 50mm to 135mm, with 85mm typically referred to as an optimum portrait lens. As always, you shouldn’t be afraid of experimenting with other lens types though! The next important part of a portrait lens will be a wide aperture, preferably f/2.8 or wider. Of course, the longer the focal length, the higher the aperture can go while still delivering a narrow Depth of Focus. Aim to keep your shutter speed at 1/100 or faster if the subject is moving to avoid motion blur.
PRODUCT PHOTOGRAPHY
As a general rule, product photography requires that the subject is completely focussed. This is because, when trying to sell a product, you want the customer to be able to see the whole thing. The acceptable width of the Depth of Field will depend on the product, but a small aperture is preferable. We’d recommend starting around f/16. As product photography is typically done in a studio, there’s a little more leeway when setting ISO or Shutter Speed. Set the ISO low to avoid noise and make up any exposure loss by lowering the Shutter Speed. Just be sure to keep the camera as steady as possible by using a tripod!
Photo by Khoman Room on Unsplash
FASHION PHOTOGRAPHY
While Fashion Photography was once a fairly set genre, the rules are no longer so heavily applied. In this sense, there is room to move when it comes to the best Depth of Field for Fashion Photography. Although fashion photography usually involves a model, it’s different to Portrait Photography because there is a product involved. For this reason, it’s ideal to have the subject entirely in focus to show off the garments or accessories being showcased. To achieve this, keep the aperture above f/2.8 if you can, but don’t be afraid to adjust the aperture as far as f/11 or smaller. Experiment with your settings and with the look, until you achieve the Depth of Field ideal for your shoot.
Photo by Kalen Emsley on Unsplash
LANDSCAPE PHOTOGRAPHY
As we said before, Hyperfocal Distance is important when it comes to optimum Landscape Photographs. This makes it hard to give a set aperture as the Hyperfocal Distance will change based on the scene being photographed and the lens being used. As a general rule though, Landscape Photography requires a Wide Depth of Field. This is much easier to achieve with a short lens, low aperture and a long focus distance. With this in mind, we’d suggest keeping your aperture between f/11 and f/22 to achieve the Best Depth of Field for Landscape Photography.
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WILDLIFE PHOTOGRAPHY
One doesn’t have to see many wildlife photographs to know that Wildlife Photography requires a very narrow Depth of Field. Surprisingly though, wildlife photographers don’t often stray below f/4. This is because it would be hard to get close to a wild animal or insect with a wide-angle lens. Instead, wildlife photographers often use lenses with focal lengths ranging from 200mm and up. And a 200mm lens would be the absolute minimum! Given what we know about focal length, this means it will automatically be easier to get a beautiful narrow Depth of Focus. However, it’s also really important that the subject is entirely in focus. This is why Wildlife Photography settings will usually start at around f/4 moving up to f/11.
Photo by Chris Kristiansen on Unsplash
JUST FOR FUN: HOW TO ACHIEVE BEAUTIFUL BOKEH (AND WHAT EXACTLY IS IT?)
Not too long ago, there was a trend on Instagram that was all about having beautiful bokeh. Cue many amateur photographers confused about comments referring to their ‘beautiful bokeh’. The word itself comes from the Japanese word for blur. Of course, seeing as you’ve made it this far, you are now well-versed in the uses of Aperture and Depth of Field.
You know that blurred backgrounds and foregrounds in any photographs are created by shooting with a wide-open aperture or with other settings that create a Narrow Depth of Field. Bokeh isn’t specifically referring to the blur of a Narrow Depth of Field though. It’s referring the pleasing circular shapes that are sometimes caused by the aperture. Beautiful and noticeable bokeh is usually created by a mix of lights and textures in the distant background of a photo. It also helps if you can shoot on a prime lens at a very wide aperture, like f/1.4.
If your head is spinning, that’s completely understandable! Who would’ve thought there is so much science behind the art of photography? Armed with a new understanding of Aperture and Depth of Field though, you’ll be ready to take your photography to the next level! If you haven’t already taken the leap from Automatic to Manual, use your new knowledge of the Exposure Triangle to help get you there. Otherwise, try some of these new techniques like Hyperfocal Distance!
