A lens is a lens is a lens, and it doesn’t know what size sensor or film gate is placed behind it. A lens projects light and the magnification size of that projection is determined by its focal length.
Nevertheless, there has always been a great deal of confusion associated with the focal length of lenses and their relationship to the size of the image area.
I’ve read many explanations in various books and on the internet over the years and authored some of them myself. But often written explanations confuse as much as they explain. If a picture is worth a 1000 words, I figure this video is equal to a small novella on the subject. Many people seem to use the various optical terms incorrectly or interchangeably, so I figured showing what happens would help demystify the concepts involved.