[John]

Hope you enjoyed your coffee Don. I can't say I enjoyed the weeding or the mowing.
The attatched diagram shows two light rays one from the top and one from the bottom of the image which are helping to form the image on the sensor. In practice the actual passage of the light is very much more complex than this but the diagram will serve its purpose.

Suppose now that we have two subjects A and B one of height Ha at distance Da from the lens and the other of height Hb at distance Db from the lens.

Then the image heights are given by:-

ha = Ha x f / Da and
hb = Hb x f/ Db

The ratio ha/hb (ie perspective) will be ha/hb = Ha x Db / ( Da x Hb)

Notice that focal length f has vanished from the equation and therefore, does not affect the ratio ha/hb (ie perspective) whereas the subject distances remain and do affect perspective.

And I wish I had never bothered!