Hiking through the Libyan Sahara in 2009, I wanted to show our guide Rhyssa (who was interested in photography) the very real consequences of different perspectives and focal lengths.
To illustrate this, I made four shots of him. In each he appears roughly the same size. (I said "roughly" - this was nothing scientific.).
But they were taken with different focal lengths (2 lenses) and from very different distances.
This exercize shows that with different lenses at different distances, your main subject may look roughly the same in size, but the relationship to the surroundings will change drastically.
Getting closer, the main subject will be distorted too, but less so in this example. (That is why some lenses are said to be flattering for portraiture.)
Here are the pictures (and I did not even use my ZD7mm lens...):