I thought I had a pretty fair idea how internally focusing lenses work, but it seems I don't completely understand what is happening with light paths and apertures.
It's my understanding that when focused very close, the focal length of an internally focusing lens actually becomes shorter, and it's angle of view is increased; much like the wide end of a zoom lens. Pupil magnification ratios and the effective f-stops also change on some lenses, like my Canon 100mm f/2.8 Macro USM lens.
I would like to find a resource that diagrams the working components of an internally focusing lens like this one, showing the relationships of the component parts, the light paths, etc., and explains how those relationships change during focusing. Can someone direct me to such a resource? Every illustrated explanation I can find about focusing just discusses externally focusing lenses, where the focal length increases at close focus.
Many thanks for any help you can provide.