透视投影与正交投影

Two maps from world to image

When each model fits

The same scene under both maps

A photographer takes two pictures of the same street. Picture A, from the sidewalk with a normal lens, shows the tram rails meeting near the horizon. Picture B, from a rooftop 300 meters away with a 600 mm lens, shows a building facade with its horizontal edges nearly parallel. Which pairing of observations and models is right?

A surveyor must measure the true widths of the windows on a flat building facade from a single photograph, with no knowledge of the window depths beyond that all windows lie on the one plane facing the camera. Which projection choice makes the measurement simplest and why?

A camera photographs a pole of world half-height $Y = 5$ with focal length $f = 100$. At depth $Z = 10$ the image half-height is $y = fY/Z = 50$. The pole is then moved to depth $Z = 20$. Using the same projection, compute the new image half-height and write the number.