Testing various fisheye capture optionsCompiled and written by Paul Bourke2006-2011
Conversion of images from OneShot cameraMay 2004
Photographic 360 degree capture devices such as the "360 One VR" manufactured by EyeSee360 and Kaidan are based upon conical mirrors mounted in front of the lens of an ordinary still or video camera. They allow one to capture the whole 360 horizontal field of view and a limited vertical field of view, typically around 100 degrees. The resulting image looks not unlike a panoramic image but with a different radial distortion. Obviously one wants to undistort these images to create more conventional views, in the discussion here that includes panoramic images, and cubic (perspective) maps. 
The suppliers of these capture devices typically provide stand alone software or plugins for other commercial image manipulation packages, eg: PhotoShop. They don't generally provide source code so that the undistortion can be integrated into a customers software. The goal of this exercise was to verify the geometric undistortion required was correctly understood and to demonstrate that with efficient and portable algorithms written in C/C++. Conversion to a cylindrical panoramic
Transformation to a panoramic image is relatively straightforward in theory, lines of longitude in the panoramic are concentric circles in the oneshot image. Lines of latitude in the panoramic are radial lines in the oneshot image. In practice the oneshot image is not necessary centered and the inner and outer ray rims need to be specified. 
Antialising is achieved using supersampling with a rectangular weighted window. The right horizontal axis of the panoramic is taken as 0 degrees longitude. Options are also provided to create a subset of the panoramic image, namely, the panoramic image between two lines of longitude. Command line usage
oneshot2pan [options] tgafile Options: -long1 n start longitude value -long2 n start longitude value -r1 n inner radius -r2 n outer radius -c x y center of cone -a n set antialias level -w n width of the output image -h n height of the output image -i apply vertical flip -d change direction Test pattern
Conversion to cubic map
oneshot2cube [options] tgafile Options: -r1 n inner radius -r2 n outer radius -c x y center of cone -a n set antialias level -w n width of the output image -h n height of the output image -l1 n latitude at r1 -l2 n latitude at r2 -i apply vertical flip Test pattern
Conversion to cubic map with a range of longitudes
Standard perspective projections can be considered to be longitude subsets (less than 90 degrees wide) taken from the cubic map. Ideally the cubic map would be aligned so that edges didn't not fall within the perspective frustum (not yet implemented). Of course one could derive the perspective views directly without using this cubic map approach.
oneshot2cube2 [options] tgafile Options: -r1 n inner radius -r2 n outer radius -c x y center of cone -a n set antialias level -w n width of the output image -h n height of the output image -lat1 n latitude at r1 -lat2 n latitude at r2 -long1 n start longitude -long2 n stop longitude -i apply vertical flipReferences
A Catadioptric Sensor with Multiple Viewpoints
Single viewpoint catadioptric cameras.
Omnidirectional vision: Theory and algorithms.
A unifying theory for central panoramic systems
and practical applications.
Nonmetric calibration of wide-angle lenses and polycameras.
The first thing one notices is that the circular fisheye, with the minimum zoom, does not fit within the sensor and it also isn't centered. The details (which may vary slightly with each camera) are shown below. While this may seem like a serious problem, for many applications it isn't. Many small planetarium systems employing a single projector and fisheye lens often only use 3/4 of the fisheye image, the portion at the "back" of the dome isn't used. Alternatively for upright domes it is common for the lower portion of the dome to be truncated (see examples later).
One solution to this is to digitally tilt the fisheye so as to remove the truncation at the bottom of the fisheye image. This technique applied to the image above is shown below, the green line shows the truncated region employed by many fisheye projection systems. Note that the image in the top half of the fisheye now does not fill the circular fisheye area, blue circle outline. This too can be corrected although unlike the tilting of the fisheye, this additional correction introduces distortion to the the upper half of the image which may or may not be objectionable, remembering that it is behind the viewer (at least in a directional dome). 
Complete example
Original frame off the Canon HV20 (movie sequence)  Centered in a circular frame fishtilt -cf 940 590 -r 724 724 -w 1280 -a 3 sample2.tga  Tilted to remove the missing front part of the fisheye fishtilt -cf 940 590 -r 724 724 -w 1280 -a 3 -t 17 sample2.tga  Non circular correction for top half of image (cheat) fishtilt -cf 940 590 -r 724 724 -w 1280 -a 3 -t 17 -b 20 sample2.tga  Truncated for offset, truncated fisheye projection fishtilt -cf 940 590 -r 724 724 -w 1280 -a 3 -t 17 -b 20 -bb sample2.tga  Further examples Two further examples are shown below, single frames extracted from a movie. These are rendered at XGA resolution (1024x768), that is, the lowest resolution fulldome projection employing a fisheye lens. It is my estimation that the quality in this case is limited by the the projection system as much as by the footage. By comparison, the quality on a HD projection system employing a spherical mirror is clearly limited by the quality of the footage. I suspect carefully captured, processed footage would be a good match for a SXGA+ based system.
Upright dome It turns out that the camera and fisheye position is more suited to truncated style upright domes. When the camera is operated upsidedown the larger part of the fisheye image missing isn't required anyway since it is below the hemisphere truncation. The smaller missing piece at the other end of the fisheye results in a small section of missing image at the very top of the dome, or it may be filled by using the same fisheye tilting procedure discussed above. Original frame off the Canon HV20 (movie sequence) Centered in a circular frame  Warped image for fulldome projection using a spherical mirror  Examples in the upright dome
Other lenses on the same camera
Nikon FC-E8:
Phoenix Super Fisheye Lens 0.25X: 
Nikon D300 and Sunex 185 degree fisheye lensMay 2008
This combination, Nikon D300 and Sunex 185 degree (5.6mm) fisheye lens, gives a full 180 degree fisheye image using more of the full frame than most other fisheye lens tested (notably Sigma lens). After cropping to 180 degree the resulting fisheye is in the order of 2580 pixels square.
The lens is certainly very solid. Extremely good focus, no manual focus required since it is fixed. I experienced very few problems even when shooting into the sun. It is not a perfect f theta lens, but then what fisheye lens is.  Perth city centre
 University of Western Australia
 20 second exposure Contribution by Alexander Mitchell A low cost option using a Lumix camera and fisheye lens results in a 1080 square fisheye at a very low price point. Of particular note is the high bit rate of 176mb/s by changing the camera firmware (by donation). Total cost is around $600 for the camera, $800 for the lens, and $20 for the Nikon m43 adaptor. 
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