Wide Angle Perspective

H. Dersch

Technical University Furtwangen


15. September 1998

In Photography the question of perspective arises when wide angle scenes have to be imaged. The normal, rectilinear perspective is technically limited to angles smaller than 180 degrees (in practice much smaller than that). Competing are the panoramic perspective, which horizontally is unlimited, vertically identical to the rectilinear, and the fisheye perspective which is unlimited in either direction.

To recover the original view, a rectilinear image has to be viewed on a flat surface, the panoramic image on a cylindrical surface, and the fisheye-image on a (near) spherical surface. In each case the viewer has to assume a well defined position relative to the image.

There are fierce debates going on (and this article arose from one) about which one is the appropriate, or most natural method. I am biased towards the answer that none is perfect and each method has its merits, but I want to provide some exaggerated example images to visualize the arguments.

The image I have choosen is a partial view of a full-spherical panorama, which is part of my  Virtual Tour of Marburg. The full view can be observed at my website. I selected a 135° horizontal part, which corresponds to the coverage of a full-frame fisheye lens (15/16mm for 35mm equipment). To roughly get the same field of view with a rectilinear lens, we need a (not-existant, but easily calculated) 7.5mm rectilinear lens, or a panoramic swing-lens camera equipped with a 16mm lens. The three images were calculated using my program "Panorama Tools" and are displayed below:

Full-Frame Fisheye (16mm)
Rectilinear lens (7.5mm)
Swing-lens or Scanning-Slit Panoramic Image (16mm lens)
While the centers of the images do not differ much, there are more drastic changes at the edges. To make this clear I have magnified an identical portion (the portrait of the young man, who happens to be my son Rick) and compared it with the usual portrait perspective (80mm telephoto lens).

Some remarks and conclusions:


Other than that it is pure personal taste and preference (probably also depending on the subject) which projection  better visualizes a wide angle scene. None does it 100% correct.  And since we all have computers today, we can simply change the projection from one type to the other as I did in this article using Panorama Tools. So in buying equipment we can choose the cheapest one (which is the Fisheye lens).

Thanks to David Ruether (ruether@fcinet.com ), who does not agree with this view, for a stimulating discussion.

Copyright 1998 © Helmut Dersch