How does the distance between stationary point and picture plane effect perspective?

Question

I want to understand what happens when you increase or decrease the distance between the stationary point and the picture plane?

I tried drawing a border (approximately 9” x 12”) on a real window with duct tape to create a picture plane (using the area within as a transparent canvas).

My goal was to see what happens when I (stationary point) moved far away. The tree that fit nicely when I was at arms length suddenly got huge when I took a few steps back and eventually only the trunk was visible in the picture plane that I made.

My question is why did this happen and how can I relate it to drawing perspective?

Answer 1

Its pure geometry. Here the draughtsman has 2 different stationary points. You see, how the apparent distance between the two observed points grows in the imaging plane as he goes further.

The distance in the image approaches the real distance when the stationary point goes very far away. The image loses the perspective because the target in this case could as well be flat.

(applied image of Albrecht Durer's woodcut "Draughtsman Making a Perspective Drawing of a Reclining Woman", the image is available freely from https://www.metmuseum.org/art/collection/search/366555)

The stick in front of draughtsman's face was intended to help to keep the stationary point constant. It's essential for consistent perspective.