What is Depth of Field and How to Use it in Your Photography

If you’ve read or watched anything about photography, you’ve likely heard the term depth of field thrown around. But what is it, exactly? This article will help you understand the term and learn how to control depth of field to take more compelling photos.

What Is Depth of Field?

The depth of field (DoF) in photography refers to the depth of the area that is in sharp focus.
There are photos where just one part of the image is in focus and the rest is smooth and out of focus. And there are also photos where everything in the frame is nice and sharp.

The depth of field is described as shallow or deep depending on how much of the photo is in sharp focus.

When a photo has a shallow depth of field, only a small portion of the image is in focus while the rest is blurred out.
A deep depth of field renders most or all of the photo in focus.
What Factors Affect Depth of Field?
There are several ways to control how much of a photo is in focus. In other words, the depth of your depth of field.

1. Aperture

One of the easiest ways to control the depth of field is to change the size of your aperture (a hole in your lens which let light through to the sensor).

When the aperture is large (small F-stop number), your depth of field will be shallow. Conversely, when you use a smaller aperture (large F-stop number), your depth of field will be deeper.

2. Distance Between Camera and the Subject
The closer you get to your subject, the shallower your depth of field.

As you can see from the example below, as you approach the subject from 5ft, 3ft, and finally 1.5ft, the DoF has gotten much shallower.

3. Focal Length of Your Lens
There is a misconception that a longer focal length (zoom lens) will yield shallower depth of field compared to a shorter focal length (wide-angle lens).

However, this is not true.

If your subject covers a similar size/portion of the frame, focal length’s effect on DoF is negligible.

However, there are practical advantages to using a zoom lens because resulting images may appear to have shallower depth of field. This is why a lot of portrait photographer’s zoom in on their subjects using a zoom lens like the 70-200mm. Longer focal lengths appear to produce shallower DOF because they have a narrower angle of view which magnify the background more to fill the frame. As a result, the out of focus background (blur) may appear more out of focus with a zoom lens.

4. Sensor Size of Your Camera
When shooting the same composition with the same aperture, an image taken with a full-frame camera results in a shallower depth of field than an image taken with a crop sensor camera. The reason is simple, to fill the frame, large sensor cameras need to either get close to the subject or zoom in (larger focal length). Both of these factors gives you a shallower depth of field.