Depth of field definition
Understanding the depth of field meaning and how to use it can drastically enhance the quality of your photos.
The captured scene always has several planes: foreground, subject, and background. By adjusting the camera settings, you can have either one plane that looks sharp while the others are blurry, or all the planes can be in focus. The former is called a shallow (small, narrow) DoF and the latter is a deep (large, wide) one.
Let’s have a look at some depth of field photography examples to better illustrate the difference between the two.
See below an example of a deep DoF, where all image details and planes look sharp from foreground to background.
And now have a look at a shallow depth of field photo, where only the bench and spruce boughs at the front are in focus. The objects behind this plane become blurred.
Here is another example of a very shallow DoF with just a piece of a postcard being crisp, while the area just in front of and behind it is fuzzy.
Have you noticed how your attention is directed to what is sharp? Do you perceive the intention of the images somehow differently?
This is what depth of field is meant for. It helps create a better composition and also adds additional meanings to your picture by highlighting interesting and important points and blurring the rest.
Depth of field usage
Many creators use a deep DoF in landscape, architecture, or real estate photography. As a rule, these types of photos need all the details to be sharp.
A shallow DoF is most common in portrait or macro photography, when we need to isolate the subject from the busy background. Sports or street photography can also use this technique to bring attention to someone or something.
However, these are not some cast-iron rules. Your creative ideas affect the choice of photography techniques.
You can adjust the image sharpness using the three main factors: aperture, distance to the subject, and focal length:
Aperture
Baseline: widen the aperture for a smaller depth of field or narrow the aperture to increase it.
Aperture is the lens opening size. It determines how much of the photo will be in focus and how much — blurry.
To get a fuzzy background around your subject, also known as bokeh, you need to open the aperture — that is, set smaller f-stop numbers, like f/1.4 or f/2.8. On the other hand, larger numbers, like f/16 or f/22, will result in images where the front and back will be crisp.
Distance
Baseline: move closer to the subject for a smaller depth of field or move away to increase it.
Distance between the camera and the point of focus can also affect DoF. As you step away, the zone of focus around the latter is getting larger. There are even various online calculators to help you play around and determine the best distance based on your settings.
Focal length
Baseline: use a longer focal length for a smaller depth of field or shorter to increase it.
The focal length describes the distance between the lens and the sensor. It can be 50mm, or 200, or 18-55mm, or some other. When you use a longer one, like 85mm or more, the objects around the subject become blurrier. A wide-angle lens, like 24mm or less, will make more of the picture in focus.
Thus, you can combine all three factors — open the aperture as much as your camera allows, come as close to your subject as possible, and use a telephoto lens — your image will have an extremely shallow depth of field. Change one or all of the factors, and you will get a medium or large DoF.
Depending on your goals you can balance these settings to produce the effect that exactly meets your intentions. Additionally, you can always enhance the effects during post-editing.