The Viewable Sphere

Look around you. Barring the effects of stereoscopy, we perceive our surroundings as a sphere centered somewhere inside our head: the viewable sphere. It is generally accepted that our eyes perceive the world in a similar way in which a pin-hole camera records a scene. This is equivalent to mapping a section of the viewable sphere (usually a region of field-of-view of at most 120 degrees) into a flat surface using a perspective projection (also known as gnomonic, or rectilinear). The perspective projection has a crucial feature: it preserves straight lines as straight. Its main disadvantage is that, as the field-of-view increases, the regions at its edges are heavily distorted. An image of field-of-view of 180 degrees would have infinite size.

Mapping a sphere (or a large portion of it) is a problem well-known to cartographers who have been interested in making flat representations of the world. They have envisioned dozens of different map projections that take the sphere and project into a plane. The choice of projection is a trade-off: one has to accept some distortion in exchange for some properties that the projection exhibits.

Photography, by its own nature, has been restricted by the optical limitations of the camera obscura and lenses (rectilinear, fisheye, and anamorphic). To overcome such limitations cinematographers developed sophisticated systems, such as Circle Vision that uses 8 cameras and a cylindrical screen to project an image of 360 degree horizontal field-of-view, but less than 90 degrees vertical. Photographers had to accept the limitations of their medium, and present wide-angle images with heavy distortions towards the edges; yet many used this feature as an artistic tool.

The computer has opened a new era in the creation of panoramas. Affordable hardware and software exists to capture and create a 360x180 degrees panorama. These spherical panoramas are usually displayed as immersive panoramas (using software such as Apple Quicktime VR) and have found an important market in surveillance and real estate, by providing a "realistic" view of a space as if one was there. Yet some photographers are interested is displaying their images flat, in a way that they can be displayed without the need of artifacts that detract from the image, or limit its access.

This exhibit is dedicated to showcase the work of these artists who are pushing the envelop in an attempt to display, in an artistic manner, a large portion of the viewable sphere in a flat plane.

I invited members of the PanotoolsNG mailing list (the largest mailing list dedicated to the discussion of panoramic images) and members of the Flickr Web site community (members of groups such as Panorama Experiments and The Lords of the Photo-Stitching) to submit their best images for consideration.

The results of this call for participation are the basis of this exhibit. I have selected the images based upon 2 main criteria: first, its aesthetic value, and second, its innovative use of projections. I have asked each artist to present along each image its equirectangular view to give the viewer an idea of the scene as it was recorded, and to demonstrate how creative these images are. When available a link to an immersive version of the image is provided

I invite the viewer to enjoy this site.

Daniel M. German
March 2007.