OK ALL YOU full frame camera fanatics

Great Bustard wrote:

Let's talk about the aperture of the lens. The f-ratio is the relative aperture, and the entrance pupil is the virtual aperture. For example, a 50mm lens with a virtual aperture (entrance pupil) of 25mm will have a relative aperture (f-ratio) of 50mm / 25mm = f/2. A 100mm lens with the same virtual aperture (entrance pupil) of 25mm will have a relative aperture (f-ratio) of 100mm / 25mm = f/4.

So, please go on about how the "lens aperture is purely a physical property of the lens, and nothing else"