One of the most popular visual effects used in music videos at the moment is a reimagining of one of the more unusual tools in a cinematographer's bag. While you wouldn't be able to create the intended use of it in post, you can mimic the creative version rather easily.
A split diopter is a filter that attaches to the front of the lens and does a more extreme very of what bifocal glasses do; it is half convex glass that makes the lens half nearsighted, allowing for a deeper focus than is traditionally possible. This has been used in a number of major films where the cinematographer would like everything in focus, despite there being too "deep" a range of subjects. That is, someone or something is extremely close to the camera, while something else of importance is far away. The area between the two subjects is often out of focus, which can make the scene a little confusing to look at.
There has, however, been a new application of this piece of cinematic equipment, and it's not for the usual practical effect. Instead, it is used to create a sort of visual echo within the frame. By changing what the split diopter is meant to be focusing on, you can create a sort of internal reflection similar to the usually undesirable visual artefact of ghosting.
In this brief tutorial by YCImaging, you can learn how to create that effect in post, quickly and to great effect. In fact, I wouldn't usually share content as short as this, but it does what most videos take ten or more minutes to do, and the results are fantastic.
