In photography, depth of field plays an essential role in the composition and aesthetic space of an image.
Thanks to it, it is you, the photographer, who chooses to give importance to the subject, whether or not to focus on it.
By mastering depth of field, you can really enhance your images by using your creative and artistic sense.
But to do this, you need to know how to control it.
So yes, you know for a fact that it’s sufﬁt to simply adjust the aperture of the diaphragm, but did you know that depth of field is inﬂuencée by other factors that you wouldn’t have thought of?
That’s what we’re going to see in this article.
I will explain to you in a clear and simple way what exactly depth of field is and how with it you can control the contribution of blur and focus on your images.
What is the depth of field in photography ?
Depth of field (DF) is the distance between the closest and furthest elements of a scene that appears to be “clearly acceptable” to the eye.
That is to say, the space that will be sharp when the picture is taken.
The extent of this sharp area is simply called the depth of field.
When you focus (MAP) on a subject and the subject becomes sharp, you should be aware that the area in focus extends 1/3 in front of (foreground sharp) the subject and 2/3 behind (background sharp) the subject.
While in macro photography, the depth of field extends identically in front of and behind the subject because of magnification.
Here are two very simple illustrations that demonstrate what I said above.
In short, everything in front of or behind the focus plane begins to lose sharpness, even though it is often not well perceived by our eyes.
Just remember that the transition from the net to ﬂou between these shots is gradual.
You should also know that the depth of field is always parallel to the sensor of your camera, which allows you to take into account the elements you want to have in the sharpness area when framing.
Therefore, determining the right depth of field is essential for successful photos, whether it is in portrait, street, landscape, sports, architecture or macro photography.
As we will see, the greater or lesser extent of this depth of field depends on three main factors that come into play at the time of shooting.
The aperture of the diaphragm
Recall that the aperture is the factor that inﬂuence most depth of field.
If you are new to photography, set your camera to Aperture Priority (AV) mode and spéciﬁez a low value (small number) to obtain a small area of sharpness (f/1.8 for example).
If you don’t have a wide-aperture lens, you can really have fun for a small price just with a 50mm 1.8.
Click here to see if you can find one for your brand of camera.
For example, a shallow depth of field is especially desirable when you’re photographing a portrait.
This allows you to isolate your subject from a background ﬂou.
Depending on the quality of your lens and in particular the number of elements that make up the diaphragm, you may be able to appreciate the quality of the background ﬂou, which is more commonly known as “Bokeh” on déﬁnit.
On the other hand, to increase the depth of field and obtain a sharpness sufﬁsante in the image, you must use a small aperture value (ex: f/8), taking care to watch the shutter speed if you photograph freehand.
To avoid worrying about exposure time, the use of a tripod is more than recommended.
Close the aperture when you want all the elements in the environment to be in focus.
This is particularly the case in landscape photography, street or architectural photography for example.
To remember these basics easily, remember that :
- The smaller the aperture number, the smaller the depth of field.
- The larger the aperture number, the greater the depth of field.
The focal length used
The second factor that affects the depth of field is the focal length you are going to use.
Long focal lengths (telephoto greater than 50mm) allow for a shallow depth of field, even at small aperture values, as shown in the picture below, taken at 400mm + f/8
Whereas if you want proﬁter to have a large sharpness area, you will have to use shorter focal lengths (wide-angle).
In other words, the shorter the focal length used, the greater the depth of field.
s you can see in the illustration below, the depth of field varies with the focal length difference, while the aperture value remains the same.
The focusing distance
The final factor that inﬂue on depth of field is the distance from the camera to the subject.
The closer you are to the subject to focus, the shallower the depth of field will be.
Conversely, the farther you are from your subject, the more likely you are to get a large depth of field.
The type of sensor inﬂuence also the depth of field
Did you know that depending on the type of camera sensor (Full format, APS-C, Micro 4/3 etc…), the depth of field is different?
I won’t go into details but to make it very simple, the bigger the size of the camera sensor is, the smaller the depth of field.
Conversely, the smaller the sensor is, the larger the area of sharpness.
This doesn’t change the way you shoot every day if you have only one camera,
because you are naturally accustomed to the influence of the sensor on the depth of field.
Simply, this notion is to be taken into account when you have to change cameras with a different sensor during a shooting.
Assessing the extent of the sharpness area with the depth of field tester
If you’ve always wondered why you can’t see the iris opening or closing when you change values on your camera, rest assured, it’s perfectly normal.
DSLR cameras have aperture or aperture presets, allowing you to comfortably have a bright and clear view at all values.
Without this function, light metering and autofocusing systems would not work well due to the lack of light caused by the diaphragm closing, especially at the smallest aperture values.
Thus, when you shoot, the aperture closes at the selected value just before the shutter opens and then returns to full aperture.
Located on the camera close to the lens, the depth of field tester is a button that allows you to remember the aperture value selected on the camera to view the depth of field before pressing the shutter release button.
For example, if you choose to close the iris at f/22, this will show you the area of sharpness at that value and ensure that all shots are sharp in the image.
This button can be very useful, especially in macro photography but also in landscape photography.
Depth of Field Calculation and Blur Simulator
To better understand the concept of depth of field, a Polish photographer and programmer named Michael Bemowski, created a feature-rich web application to calculate depth of field and simulate bokeh.
This can help you see how it works in practice by changing parameters such as focal length, aperture, sensor size, camera to subject distance, subject to background distance and framing.
With this online application, when you change your shooting settings, a picture will be updated in real time on the right side to show you how the depth of field is affected.
On top of that, the simulator calculates the depth of field and allows you to view it at the bottom of the application.
Finally, the Dof Simulator application allows you to save your settings.Click here to test this depth of field simulator.
If you want to use this application on your phone, you can change the presentation to a mobile version by clicking a button on the screen.
The Android version is also available at this address.
You can also run this application offline by downloading it below.
Windows Installer and mobile version Mac OSX
32-bit and 64-bit Linux
Be aware that the notion of depth of field is much more complex than that, as Dof Simulator demonstrates.
Some of the terms used that I haven’t mentioned are technical and physics related.
For me, they are not essential when you practice photography.
Nevertheless, the fact of calculating the depth of field can be useful in landscape photography to know the hyperfocal distance but also to determine the area of sharpness in macro photography.
I wished to go to the essential by sharing the most elementary basics with you.
Finally, remember that depth of field is an artistic tool at the service of your images and that only you have the power to use it with subtlety depending on the subject you are photographing.