For example. A perspective from Keith Adams

By Mike Seymour:

As a compositor, I am often asked to shoot elements to match existing footage or stills. Unlike shooting all original elements where camera placement, lens, tilt angle, etc. can be logged and reset in multiple locations. Existing footage and stills most often do not come with camera data. Using a few perspective tools to deconstruct footage can provide a close approximation of camera placement, framing and focal length on set.