Focal length and Perspective
Technology - Technology
The following slide show illustrates the effect of different focal length on the perspective. Please note that the lamp has the same size on film for every focal length (so I moved my position according to the focal length as opposed to "zooming"). Just click on the different focal lengths below the picture and see what happens (this requires Javascript).

So what can you see ? The longer the focal length the more jumps the church (background object) towards the lamp - the perspective gets COMPRESSED. On the other hand the wide and especially the ultra-wide angle setting moves it away thus creating DEPTH. The 50mm setting represents the perspective as you can see it with your naked eye.