Wilt, I know this is an old post and I've read "most" this this thread and I have a question that I hope has not been already asked and answered.
Is the phenomenon that you describe above enhanced even further when the distances between the 4 objects increases?
The reason I ask is that when I lived on the west coast a few years back I noticed a strange thing happening. Lets say that "A" was a pier I'm shooting while standing on the beach in White Rock BC. The "other item" is Orca Island 10 or 15 miles out to sea.
As I moved back off the beach to location B and even further up to 4 miles back (and higher in elevation) I noticed that Orca Island seemed to be getting bigger. As a matter of fact I could see a lot more detail, such as the cell towers and antenna on top of a hill on the island that I could not make out when I was on the beach at sea level.
It seems that moving back (a couple of miles) as well as up ( 500 or 600 feet) seemed to exaggerate amount the background item grew in size.
Your thoughts? (Great thread, by the way)
I wrote the following near the end of the first post in this thread. It should answer your question.
Let's assume that you are taking a photo of some friends in a scene that has mountains in the background. You stand 20 feet from the people and view the scene. A 50mm lens will let you fill the frame with the group of people and some of the background quite nicely, so you take a shot. Then you realize that the mountains are rather small in the background.
Back up to to 40 feet (twice the distance) from the group of people and view the scene, you will see that the mountains are now larger relative to the people - twice the size they were before, in fact. However, the people are smaller in your viewfinder. You now need a 100mm lens to keep the people the same size as in the first image, but the mountains now appear twice the size that they were in the first shot.
Why is this? It's because the additional twenty feet that you put between yourself and the people is insignificant relative to the fifteen miles between your viewing spot and the mountains.