The fact that the depth of field varies depending on focal length seems pretty straightforward, doesn’t it? Matt Granger however says that wide angle lenses don’t necessarily have a smaller depth of field when compared to longer telephoto lenses:
To understand any of this, you have to know what depth of field is: (Yes, this is very basic) Depth of field is basically the depth of your image that is in sharp focus, it is usually about 1/3 in front of your focus and 2/3 behind it.
In his video, Matt conducts a test to prove his point: He takes the same shot with the same framing and only changes the focal length and the position of the camera. The aperture was kept the same – f/2.8 – throughout the shoot. Of course when changing the focal length of your lens you’ll have to physically move the camera if you want your final result to have the same crop.
Here are the results: