Zoom and perspective

I spent some time to get the mouseover code to work. In the end I used the code from http://www.htmlite.com/JS019.php as it was the shortest and simplest. I took so long because the preview function doesn't work, in preview the code didn't work but it works now, as you can see.

I'm trying to investigate tricks of photography. Here, I'm figuring out how to take pictures so people look smaller, which is what everybody wants. In which image does the water bottle look smaller? Actually, it's about the same size in both images. It's the background that changes. This is done by changing the focal length (zoom) of the lens, and moving the camera nearer/further away to keep the subject (the water bottle) the same size.

The first image uses 18 mm focal length and the second 55 mm (×1.5 for my camera's DX sensor). Apparently, to make the subject look smaller, use a longer focal length and stand further away. I suspect the effect depends on the distance from the subject to the background. If the subject is flat against a wall, it won't make any difference.

A similar effect in video is the dolly zoom, say when a character realises his lover is his sister, the background creeps up/away from him. This is done by changing the zoom and moving the camera so the subject remains the same size while the background changes.
Further reading: The Straight Dope on why people look fatter on camera.