Learn how the Depth of Field in Photography works
When looking at photographs, one thing that becomes very obvious, even to people that have no idea about photography is the depth of field. Most people have a different outlook on the depth of field. I have even heard of people that photographed with a mobile phone, that they were annoyed, that their new and expensive camera wouldn’t display everything sharp.
Others are thinking that the smaller the depth of field is and the more area is blurred out in a picture, the higher quality the gear must be.
But are these opinions true and which factors are influencing the depth of field? What does it mean when people are getting crazy over “BOKEH” and how does the depth of field influence Street Photography?
I want to answer these questions and show You how the depth of field in photography works and how You can use it in Your creative process.
What is the Depth of Field
A picture has multiple elements and zones in it. There are areas that are crystal clear and sharp, while other areas seem to be blurred out. The Depth of field can be described as the zone, that presents a sharp image to the viewer. This zone can be larger or more narrow depending on the camera settings and other circumstances.
On the other hand, there are various reasons why an image appears to be blurred and not sharp at all. For example, You could have shaken the camera, or using a too long shutter speed while shooting hand-held. This means, that the whole picture will be blurred and this doesn’t have to do anything with the fact of the depth of field.
Then, You can also just miss the focus and the whole picture can be blurred as well. Those are mistakes and not what the depth of field describes.
The depth of field is a willing use of sharper and unsharp areas in a picture. With the depth of field, the photographer is able to focus the attention to a certain detail, while blurring out the surrounding, or background.
When it comes to the depth of field, there is no right and wrong and it depends on the creative process and what You want to achieve. You can broaden the acceptable zone that is sharp, to show the viewer more of the picture, or You can narrow the zone to a very narrow spot and almost blur everything. This is up to You and Your style of photography.
In the following, I want to explain, how You can influence the depth of field, to come closer to the style of picture that You want to achieve.
Influence Factors of the Depth of Field
One prejudice when it comes to the depth of field and bokeh is, that You need super expensive gear to achieve a very narrow depth of field and good-looking bokeh. While this may be true in very special circumstances, the price difference of a lens that offers an aperture of f/1.8 to f/1.2 for example isn’t justified in my personal view. The difference can often be in the 4-digit areas and while You can get slightly improved image quality, the price increase is seldom justifiable.
Instead of investing in the most expensive gear, have a look at how You can influence the depth of field and bokeh with easier means.
Aperture
The aperture has a major influence in the depth of field. You could break it down and make a whole university class about this subject where one could explain the connection between the aperture and depth of field very thoroughly. Since there is no exam and You probably don’t want to take this test anyway, I explain the influence of the aperture on the depth of field more from a practical point of view.
I have explained how the aperture influences the final image in-depth before, so if You want to have a deeper understanding, this article about the aperture in photography will help You out.
The aperture can be compared to the human eye. As humans, we can not willingly control our “aperture”, but the eye will make the adjustments automatically. The brighter the light is, the smaller the pupil will become. With the help of this reaction, our body is able to regulate the amount of light that enters the eye very accurately. The darker the environment is, the wider the pupil will get and more light is able to enter.
With the camera, You can also regulate the light that is entering the camera sensor with the aperture. But the aperture has also a second effect. The more closed the aperture will be, think about f/8 or f/16 for example, the wider the depth of field will be.
Contrarily, if You open the aperture for example at f/1.4, the depth of field will become more narrow.
The reason behind this is that less light will hit the outside of the lens. For a more thorough explanation, I recommend the article on Wikipedia.
As a personal anecdote, as a short-sighted person, I can to some extend narrow the pupil to create a broader depth of field. Maybe You are in class and see some people squinting because the text on the board is difficult to read. Then the reason behind this may be that they are short-sighted and broaden their depth of field by squinting.
The more open the aperture, the narrower the depth of field.
The less open the aperture, the broader the depth of field.
Focal Length of the Lens
The lens has a huge influence on the depth of field. Not really in the context of the quality of the lens, but that the focal length does make a huge difference.
With a wide-angle lens of around 28mm, it will be very difficult to create a narrow depth of field. Even if You use a 28mm lens with an aperture of f/1.2, the subject needs to be very close, to create a narrow depth of field.
A 35mm lens lets You create some bokeh and a narrow depth of field will be easier to achieve, but You still need to use a wide open aperture.
When going to the range of telelenses, let’s say anything above 55mm, it will be a lot easier to get a narrow depth of field. Even with an aperture of f/2.8, You can create greater blurred out areas.
The shorter the lens, the more important it will be, that You use a lens that allows You to shoot wide open at f/1.4 or even better at f/1.2.
For comparison, here are some focal lengths and apertures and their respective depth of field, calculated with the DOF tool that You can use for free.
For this example, we are using a Canon 5D Mark III and the subject is 10 meters away.
With a 55mm lens and an aperture of f/2.8, the total depth of field is around 6 meters.
Changing the 55mm lens to 35mm and opening the aperture to f/1.8 gives us a total depth of field of more than 10 meters.
If You are having a wide-angle lens of 23mm and the aperture is at f/1.2, the total depth of field is around 25 meters.
You can see, even though the aperture got more open by a very wide margin, the depth of field still got broader, meaning that more area is sharp and in-focus.
With a steady aperture of f/2.8 and just changing the focal length, You get the following depth of field ranges.
55mm — 10 meters
35mm — 26 meters
23mm — Infinite
At 23mm, we hit the hyperfocal distance and everything after the near limit of 3,85 meter will be in-focus.
Subject Distance
The third big influencing factor on the total depth of field is the subject distance. To get a better understanding of this, I would use the DOF tool again and play around with the subject distance a bit.
In short, the closer the subject is and the shorter the focusing distance is, the narrower the depth of field will be.
So if You have a wide-angle lens and still want to create a blurred out background, You need to get closer to Your subject.
Sensor
Ever since the introduction of cameras, there were different formats. In analog photography, the 35mm crop size has claimed to be the standard sensor since.
However, when digital cameras were introduced, there were a lot of different sensor sizes. The 35mm sensor size is called the “full-frame” standard and is somewhat the base of every calculation.
When talking about consumer cameras, the APS-C sensor and the Micro Four-Thirds standard has also become more popular. Those sensors are smaller than the full-frame sensor. The APS-C sensor has a crop factor of 1,6 and the Micro Four-Thirds sensor of 2.
The crop-factor will effectively change Your focal length. Usually, lenses are bound to one mount and cannot be swapped around between the different sensor standards.
Some Sony models can be swapped between their full-frame camera sensors and their APS-C camera models. If You take a 35mm lens and put it on the Sony A7RII, the effective focal length will remain at 35mm since it is a full-frame camera.
If You put the same lens on the Sony A6000, the field of view of the 35mm lens will change to a 55mm lens. Now we would expect that the effective focal length of 55mm would produce a shallower depth of field.
However, the depth of field stays roughly the same.
The reason for that is, that larger sensors produce a wider depth of field.
Calculating the Depth of Field
You probably don’t need to calculate the exact depth of field in any of Your jobs as a photographer, or when You do it as a hobby. But playing around with some numbers can help You to get a better understanding of this subject.
So far, You might have read the article, but some factors and how it does change may not be totally clear to You. To get a better grasp of understanding how the depth of field will change, You can use some online tools.
One of the more simple tools is the one from DOF Master. There You can choose from different camera models, the focal length, aperture, and subject distance. In the results, You will get a comprehensive overview of the different numbers. This is a great tool to see very quickly, which influence the different aspects of the camera has.
The DOF Master tool works great, but it does seem a bit outdated from a visual standpoint. If You want to see a more complex simulation of the depth of field and how it does change depending on Your input values, I recommend You to use the DOF Simulator. The advantage is, that there is a sample image that will show how the depth of field is affected by Your input values. In addition to just showing different numbers, You will see visually how the depth of field changes.
How to set the Depth of Field on Your Camera
The depth of field is the result of the mentioned influence factors. You cannot go to Your camera settings and say that the depth of field should be a certain value. Controlling the depth of field is very closely related to other complex fields like the exposure triangle, where I present some great infographics about the exposure and depth of field in photography in the linked article, to give You a better overview of the exposure and depth of field.
While You cannot set the depth of field on Your camera with a simple dial, You have of course some influence. There are three basic options You can change on Your camera. The Aperture, shutter speed, and ISO. The influence of the aperture should be known to You by now. The shutter speed and ISO don’t have a direct influence on the depth of field. The depth of field will remain the same, no matter if You shoot at 1/200s or at 1/1000s. Same goes for the ISO, it doesn’t affect the depth of field.
The only setting that affects the depth of field is the aperture. So if You are on a location and taking portrait pictures and suddenly realize that the background is not really great, You should either find a better background or open the aperture to blur more of the background.
Keep in mind though, that according to the exposure You now have to either shoot with a faster shutter speed or a lower ISO to avoid overexposing the image.
The second way of changing the effective depth of field would be by using a longer focal length. If You have the option to either change the lens or use a zoom lens, then using a longer focal length will narrow the depth of field as well.
The final option to change the depth of field would be to get closer to Your subject. This does change the frame and might not be ideal if You are already doing a full body portrait or want to capture a lot of the surroundings. But if You are doing a headshot, going closer will give You a lot more options for a narrower depth of field.
While You cannot set the depth of field on Your camera, some models have indicators that help You. For example, my RicohGR II has the depth of field integrated into the LCD display and it does show me the acceptable focus range.
Benefits of a shallow Depth of Field
The depth of field is a creative tool that You can use in photography. It does have a lot of benefits and having a shallower depth of field can make the image more interesting.
The main reason for using a shallow depth of field is to steer the attention of the viewer to a certain point. If the whole image is in-focus, it can be harder for the viewer to know which detail You actually want to show. This does make it more difficult to tell a story and since photography is all about the story, pictures that don’t have a clear focus appear to be more chaotic or just “random”.
The depth of Field is not the only means to lead the attention though. There are other compositional elements like leading lines or the rule of thirds, which are also an important element of every composition in photography.
When using a shallow depth of field, You shouldn’t think that You can just ignore every other compositional aspect because it will be blurred out anyway.
Sometimes, a shallow depth of field in combination with some light sources in the background can simply look good. It doesn’t really add anything to the story, but this unsharp background is what Bokeh is usually referred to and while it may look a bit “cheesy” it still can enhance the appearance of the picture.
When to use a wider Depth of Field
Some people might think that the lens can only be used in the most open setting. Of Course, a lot of people justify their purchase of an expensive lens, that has a wide aperture, by using it wide open at any time.
There are many situations where a wider depth of field is beneficial for the picture and should be used instead of blurring out most of the scene.
As a Street Photographer myself, I find that by using a wider depth of field, I am able to create a more complex story and it is easier to see the environment and how it does add to the scene itself. Using a very shallow depth of field would mean, that most of the scene is hidden and that is not really what Street or Documentary Photography is about. The context of the scene is also important and not the subject alone.
Of course, I agree that Street Photography does become more difficult when using a wider depth of field. You have to arrange the picture more carefully and the background can make or break a picture. I have shown plenty of tips on how to improving the background if this is one of Your problems. But narrowing down the depth of field is surely no solution to this problem.
Leading the eye and the center of attention does become more difficult and surely it is no easy task, but rather than blurring out most of the information, try to compose the image in a way that the viewer can still follow the story even though most of the image is visible.
Also, think about the important aspect of Documentary Photography to show human life at a certain time. If all we would see would be the subject and we wouldn’t be able to see its surroundings, there would be a lot of information that is lost. So when it comes to Street Photography, rather keep a wide depth of field.
Other genres, where a wider depth of field is usually beneficial is landscape photography and astrophotography. In astrophotography, Your subject is so far away that it isn’t really possible to work with a narrow depth of field. The hyperfocal distance will always be reached.
In landscape photography, the subject is rather wide-spread and a huge area should be revealed. Using a wide depth of field does increase the perception of depth and shows the beauty of nature more detailed. You can still play with some blurry details, for example by placing an object in the front, like a rock or a tree.
Depth of Field and Zone-Focusing
Understanding how the depth of field works has practical advantages.
Does the focus not work as You want it to, or are You photographing in a field that requires to be very quickly?
In Street Photography, we have to make decisions very quickly and waiting for the auto-focus to find the sweet spot is not always applicable. Sometimes, we also shoot from the hip and don’t even look through the viewfinder.
All of these are cases, where we benefit from a broader depth of field. The broader the depth of field is, the larger the margin of error can be.
For a more in-depth technique that will get You sharp images, I have explained the Zone-Focus technique for Street Photography.
With Zone-Focusing, You set the focus to a certain distance and use a wider aperture to broaden the depth of field. Thanks to the manual focus, You don’t have to rely on the auto-focus anymore and can just let the focus remain on the fixed distance.
Without having to think about the focus anymore, You can totally concentrate on the picture.
Can the Depth of Field “heal” my Pictures?
The final misconception that a lot of photographers have and plays a huge part in why a narrow depth of field is used in a lot of cases, is that it can save a bad picture.
Taking a picture is easy, it only requires You to press a button and the camera will capture the scene. Modern cameras are even so helpful to assist You when it comes to focusing or the exposure.
What they can’t do is helping You creating good pictures that are great when it comes to the compositional elements.
When problems arise and the background doesn’t work, is disturbing and draws the attention away from the subject, then one of the first reactions would be to open the aperture until the background isn’t visible anymore.
While the more narrow depth of field can now smoothen the chaotic background a little bit, it doesn’t take anything away from the fact that the background just doesn’t work in this situation.
Opening the aperture won’t magically make Your pictures better.
Instead, You should learn how composition in photography works and make the picture better in the “natural” way and not by using a shallow depth of field.
Key Findings of the Depth of Field
The Depth of Field describes the phenomenon, that not all areas of a picture are crystal clear and sharp. Depending on different factors, a lot of the area can be blurred out.
In this context we are speaking about the depth of field as the area, that is still in acceptable focus and clearly visible. A narrow Depth of Field describes a picture, where most of the area is blurred out, while a wide Depth of Field means, that most of the picture is clearly visible.
The influence factors are:
- Aperture
An aperture of f/1.8 produces a more shallow depth of field, while at f/11 a greater area will be sharp and in-focus.
- Focal Length
The longer the lens is, the more narrow the depth of field will be.
- Sensor
A full-frame camera does have a more shallow depth of field, than a camera using an APS-C sensor.
- Subject Distance
The closer the subject (and therefore the focus distance) is, the more shallow the depth of field will be.
A shallow Depth of Field is often used to lead the attention to the subject of the picture. As a viewer, it does become immediately clear where our attention should be. This technique is often used in Portrait Photography, or during the night when lights in the background create an outstanding “Bokeh”.
For other genres like Street Photography, or landscape photography, a wide depth of field is usually the goal. With the wide depth of field, You can show more of the picture and it does have a more complex feeling to it.
Whichever depth of field You prefer is ultimately up to You. You can do Street Photography with an open aperture, as well as landscapes. But one thing You should remember is that a shallow depth of field is no excuse for a faulty composition. Whether You use a shallow depth of field or a wide one, You should always try to achieve the best composition and background that is possible.
Anything else is Your freedom of creativity and how You want to use the depth of field.
