When I started to investigate making Spherical (360°) Panoramas everything I read suggested that a fisheye lens was essential, but the reality is that, in theory, almost any lens (camera) can be used, although there are some things to take into consideration.
It is helpful to have manual functions on the camera to control such things as exposure, focus and white balance. Letting the camera autofocus and/or automatically select the exposure can result in a less than satisfactory outcome.
The wider the angle of view (coverage) of the lens, the fewer images are required and the better chance of sufficient detail in the overlaps for the processing software (e.g. PTGui) to generate good Control Points. The fewer the images required the less time is needed for taking the photographs and creating the Spherical Panorama, although the increase in times is not significant when compared with getting to the site, setting up and downloading and working on the images.
The more accurately the lens can be rotated around the Nodal Point and aimed in the required directions at the required intervals the better, especially if the lens has a small angle of view so that a lot of images are required.
From these requirements it can be concluded that a DSLR (Digital Single Lens Reflex) camera, fisheye lens and panoramic head are needed to take Spherical Panoramas, but these are not "low cost" items and a fisheye lens could cost more than twice the DSLR body, although lower cost fisheye lenses are now becoming available. Of these 3 items I would suggest that the first one to acquire is a panoramic head as this will enable the taking of the images with almost any lens (camera). It is worth investing in a panoramic head with positive and precise "click stops" such as the Nodal Point NN3 rather than a friction type head, especially if you are starting off with a compact camera or DSLR with a normal (rectilinear) lens.
Good results can be achieved with a compact camera with a normal lens and this can be an inexpensive entry into the fascinating world of Spherical Panoramas. In an investigation to se the differences between creating Spherical Panoramas with different lenses, the results from a Panasonic Lumix DMC-FX100 were not a lot different than using a DSLR with a range of lenses although 64 photographs were taken and I resorted to using flash because of the lack of manual controls on this camera. It is also possible to greatly reduce the number of images required with a compact camera by using a relatively inexpensive fisheye lens such as the Ipix.
Most DSLR sold with a "kit" lens have a lens with a minimum focal length of 18mm, which is also capable of taking excellent Spherical Panoramas as shown in the investigation to se the differences with different lenses. The times for processing the images will depend on the specification of the computer used and the dedication of the computer to the task. If other programs are being used or running in the background, or the computer is on-line, then the processing will take longer.
The following table gives an idea of the difference in time, using PTGui and Pano2VR, for processing the 12 images using the Nikon 10.5mm fisheye lens compared with 56 images using the Nikon 18-200mm lens @ 18mm:
The operations to Open Images and Align Images are pro rata with the number of images, whereas the creation of the Panorama from the 56 images only took twice as long as the creation of the Panorama from the 12 images.
For a DSLR user considering the purchase of a fisheye lens to reduce the number of images required for Spherical Panoramas it may be worth considering a normal (rectilinear) short focal length lens or short focal length zoom lens, such as the Sigma 10-20mm, which is almost half the price of a Sigma 8mm fisheye lens, and much more versatile for "normal" photography.
The following table gives an idea of the difference in time, using PTGui and Pano2VR, for processing the 10 images using the Sigma 8mm fisheye lens compared with 24 images using the Sigma 10-20mm lens @ 10mm, showing that the time differences are not significant:
A lens such as the Sigma 10-20mm is a very suitable lens for Panoramic Photography because it has a single Nodal Point for a given focal length, which does not move as the lens is focused, unlike the fisheye lenses where the Nodal Point moves towards the front of the lens as the angle of view increases and as the lens is focused from infinity to close focused. I tend to err on the side of more overlap (50%) and more "directions" than is probably necessary on the basis that I do not wish to have to retake the photographs, which may not be possible anyway, and found that the following arrangements gave me the best results:
I did find that Sigma 10-20mm zoom also worked fine with 6 directions at 60° intervals in each of the 3 planes, which redeuced processing time, and suspect that this is due to the excellent geometry of the lens with its single Nodal Point.
Setting up the camera/lens on a Panoramic Head
The first task is to check the location of the tripod bush (the ¼ inch Whitworth thread) in the camera's base plate. If you are using a DSLR the chances are that this is in "in line" with axis of the lens (i.e. if the camera is placed on a horizontal surface the axis of the tripod bush is in the same vertical plane as the axis of the lens), in which case no additional consideration is need for this, but the chances are that if you are using a compact camera that the tripod bush is offset, in which case a "device" will be needed to ensure that the axis of the lens is in the same horizontal plane as the point of rotation on the upper arm of the Panoramic Head as in the case of the Panasonic Lumix in the following photographs, shown by the green line. This is especially important if the camera is to be tilted away from the horizontal, which will be the case when using a normal (rectilinear) lens.
The lower rail of the Panoramic Head is used to align the axis if the lens with the vertical axis of rotation of the Panoramic Head as shown by the red line in the above photographs. Once this has been set for a particular camera it will always remain the same as the distance from the camera base plate to the principal ray of the lens is a constant.
The upper rail can then be used to align the lens so that the Nodal Point (entrance pupil) of the lens coincides with the vertical axis of rotation of the Panoramic Head as shown by the red line in the following photographs.
The above left photograph shows the Panasonic Lumix, which has the tripod bush approximately in line with the top of the top rail necessitating a device, such as a T adapter, to bring the lens axis into the same horizontal plane as the point of rotation of the upper arm. The central photograph shows a Nikon 18-200mm VR lens set at 18mm where the Nodal Point is 32mm back from the front rim of the lens, and the right photograph shows a Nikon 10.5mm Fisheye lens where the Nodal Point is not a single point so the lens is set to align the gold ring with the vertical axis of rotation of the Panoramic Head.
The two following photographs show a Sigma 10-20mm lens. In the left photograph the lens is set at 10mm where the Nodal Point is 6mm back from the gold ring. When the Sigma 10-20mm lens is zoomed to the 20mm setting the Nodal Point coincides with the gold ring so the vertical axis of rotation of the Panoramic Head should coincide with the gold ring. However, there is insufficient space on the upper rail of the Nodal Ninja NN3to to accommodate this so the photograph shows the lens incorrectly aligned. It is probable that if such a lens is used it is set to the widest Angle of View to minimise the number of images required for a Spherical Panorama, but this misalignment can be overcome by using a T adapter, in which case the lower rail would need adjusting to bring the lens axis back into alignment with the vertical axis of rotation of the Panoramic Head.