I believe you already know that “zooming with your feet” and changing the focal length can affect the relationship between your subject and the background. In this short video, you can see the effect of both coming close to the subject and changing the focal length, and how it affects the final look of your image.
The video was posted by dubby8880 on Reddit, and it’s one of those amusing short demonstrations of the focal length change. A tree is the main subject, the video starts with moving to the tree physically, without changing the focal length. In the other part, the photographer moves away from the tree while zooming in. Or rather simulates this effect by cropping and scaling (considering that the video is a collaboration between Ari Fararroy and Adobe). This makes the tree stay about the same size in the frame, and the background changes and becomes more compressed. This creates the dolly zoom effect you can see in movies such as Vertigo and Jaws.
We’ve seen before how different focal lengths work for portraits and headshots. And there’s an example here how focal length affects the depth of field. If you’re interested to read more on zooming with your feet versus zooming with your lens, make sure to check out this article and watch Jay P. Morgan‘s video below for some great examples.