Depth of field in landscape photography
Depth of field is probably one of the most important technical issues in landscape photography. It can be a complicated issue for beginners and even for more experienced photographers. There are many guides and rules of thumb about this matter, many of them are not very accurate and might not result with the best outcome you can get. In this article i'll try to explain Depth of field (DOF) in the best and simplest way so you can understand how to use it!
what is depth of field?
Depth of field (DOF) describes the area in a photo which is in acceptably sharp focus. It is basically the distance from nearest to the farthest areas in the photo which is acceptably sharp.
In landscape photography we usually thrive to achieve very large or infinite DOF which will make all the parts in our photo look sharp, from the foreground to the background. There is absolutely no rule that determines that a landscape photo should always be sharp from foreground to background, but it usually the case and it is important you know how to achieve it if that's what you want.
what factors determine the depth of field?
Depth of field (DOF) is basically determined by three factors: focus distance, focal length and aperture.
Focus distance - is the distance on which you set the camera to focus. Generally - short focus distance will result in shallow DOF and far focus will result in large depth of Field, BUT it is not completely accurate. To understand it more accurately wait for the explanation about Hyper-Focal distance which will be explained below!
Now lets make another important distinction: the distance on which you set the focus will always be sharp! any other area in the photo which is in the same distance will also be sharp, even if you didn't focus on it! Lets say for example you focused on a person which stands 2 meters from you - any other person or object which is 2 meters from will also be sharp, because focus works for distance. The depth of field (which depends on focus distance + focal length + aperture) will determine how much area before and after the focus distance will also be acceptably sharp. So more specifically, depth of field is the area before and after the focus distance which is acceptably sharp.
It is highly recommended to use one focus point while focusing so you can determine exactly where the focus will be. People some times get confused and think that selecting many focus points will result in large DOF which not true. I only allows the camera to select the focus distance from several areas, but in the end it will focus on a specific distance, which might not be what you wanted.
Focal Length - is the current focal length you use when taking the picture. Short focal length (wide angle lens) will result in larger DOF, Long focal length (Telephoto lens) will result in shallower DOF.
Aperture - is the current aperture you use when taking the picture. A wider aperture (small F stop number) will result in shallower DOF, a narrow aperture (large F stop number) will result in larger DOF.
review - factors that determine depth of field
Large DOF - generally if you want to create large DOF you should use short focal length, narrow aperture and long focus distance (again, wait for more accurate explanation about hyper-focal distance).
Shallow DOF - generally if you want to create shallow DOF you should use large focal length, wide aperture and short focus distance.
Depth of field calculator
The best way to know the DOF when taking a photo is to use a DOF calculator. You can find DOF calculators in online websites and also in smartphone apps. With a DOF calculator you can set the factors of focus distance, focal length, aperture and know exactly what will be the DOF in your photo (You will also need to set the camera you're using because the sensor size affects the "real" focal length). After setting all the factors, you will be able to see the nearest to the farthest distance the photo will be sharp.
Hyper focal distance
After understanding the basics of DOF, I'll explain in this section about the most accurate way to determine the lagest DOF you can achieve when photographing landscapes. This subject is also very important for Astrophotography.
The Hyper-Focal distance - is the nearest distance you can focus on and achieve sharpness that includes the background (depending on the current focal length and aperture you use). Meaning it is actually the largest DOF possible to achieve in one shot. Knowing the hyper-focal distance requires using the DOF calculator. All you have to do in order to know the hyper focal distance is to set the focal length and aperture. You can use this DOF calculator for example, open it in another tab and try to following examples:
- Lets say we're using a full frame camera, with a 16mm lens and F/8 aperture. After setting these factors, you will see the hyper focal distance is: 1.08 meters. If you also set the focus distance to 1.09 meters you will see the DOF starts from 0.54 meters all the way to infinity.
- Lets say we're using a full frame camera, with a 16mm lens and F/22 aperture. After setting these factors, you will see the hyper focal distance is: 0.39 meters. If you also set the focus distance to 0.4 meters you will see the DOF starts from 0.2 meters all the way to infinity.
- Now lets say we're using the same settings like the last example, but now set the focus distance to 20 meters instead of 0.4 - what happens to the DOF? you can see it now starts a bit more far at 0.37 meters (instead of 0.2) and ends at infinity, meaning we lost some sharpness in the foreground. in this case it really isn't problematic because we still have very large DOF, but depending on the setting you use, it might be critical.
Generally speaking, when using wide angle lenses and narrow aperture you instantly get very large DOF which makes everything very easy. You can almost blindly focus to 1-2 meters and be confident the whole photo will be sharp from foreground to background. That's why in most cases when using wide angle lenses and narrow aperture you won't need to bother and check the DOF. Understanding DOF and the hyper-focal distance is still important for other cases in which you might use settings that create shallower DOF like using a Tele lens or using a wide aperture for Astrophotography/night photography.
Wide angle lens examples:
Sunrise at the Dead Sea, Israel | Shot with a Canon 5D mark III (Full frame), 17mm focal length, F/11 aperture. The close salt formation in the foreground was a bit closer than a meter to the camera.
Sunrise at Palmachim beach, Israel | Shot with a Canon 6D (Full frame), 16mm focal length, F/22 aperture. The close rock was about 0.6 meters from the camera.
Glacier lagoon, Iceland | Shot with a Canon 5D matk IV (Full frame), 16mm focal length, F/16 aperture. The close ice formation was about 0.4 cm from the camera.
Telephoto lens examples:
Sunrise at DeadVlei, Namibia| Shot with a Canon 5D mark IV (Full frame), 135mm focal length, F/5.6 aperture. The close tree was about 150 meters from the camera.
Alpe Di Siusi, Italian Dolomites | Shot with a Canon 5D mark III (Full frame), 70mm focal length, F/8 aperture. The tree area was about 2,500 meters from the camera.
Sossusvlei sand dunes, Namibia | Shot with a Canon 5D mark IV (Full frame), 380mm focal length, F/6.3 aperture. The tree area was about 270 meters from the camera. This photo did not require infinite DOF because the dune was 5 to 50 meters behind the tree.
Mastering DOF is very important as part of mastering the whole technique in landscape photography. It can be a quite complicated subject that takes time and practice to understand, but it is worth it. Most beginner photographers who practice landscape photography with wide angle lenses usually do not need to understand DOF very deeply, but as you dive in and try more areas like Telephoto lenses of Astrophotography, it is more important to understand and use DOF accurately.
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