Panoramic photography 全景摄影

                
                
Panoramic photography is a technique of photography, using specialized equipment or software, that captures images with elongated fields of view. It is sometimes known as wide format photography. The term has also been applied to a photograph that is cropped to a relatively wide aspect ratio. While there is no formal division between "wide-angle" and "panoramic" photography, "wide-angle" normally refers to a type of lens, but using this lens type does not necessarily make an image a panorama. An image made with an ultra wide-angle fisheye lens covering the normal film frame of 1:1.33 is not automatically considered to be a panorama. An image showing a field of view approximating, or greater than, that of the human eye – about 160° by 75° – may be termed panoramic. This generally means it has an aspect ratio of 2:1 or larger, the image being at least twice as wide as it is high. The resulting images take the form of a wide strip. Some panoramic images have aspect ratios of 4:1 and sometimes 10:1, covering fields of view of up to 360 degrees. Both the aspect ratio and coverage of field are important factors in defining a true panoramic image.
                
                
An 1851 panoramic showing San Francisco from Rincon Hill by photographer Martin Behrmanx. It is believed that the panorama initially had eleven plates, but the original daguerreotypes no longer exist.
History
One of the first recorded patents for a panoramic camera was submitted by Joseph Puchberger in Austria in 1843 for a hand-cranked, 150° field of view, 8-inch focal length camera that exposed a relatively large Daguerreotype, up to 24 inches (610 mm) long. A more successful and technically superior panoramic camera was assembled the next year by Friedrich von Martens in Germany in 1844. His camera, the Megaskop, added the crucial feature of set gears which offered a relatively steady panning speed. As a result, the camera properly exposed the photographic plate, avoiding unsteady speeds that can create an unevenness in exposure, called banding. Martens was employed by Lerebours, a photographer/publisher. It is also possible that Martens camera was perfected before Puchberger patented his camera. Because of the high cost of materials and the technical difficulty of properly exposing the plates, Daguerreotype panoramas, especially those pieced together from several plates (see below) are rare.
Following the invention of flexible film in 1888, panoramic photography was revolutionised. Dozens of cameras were marketed, many with brand names heavily indicative of their time. Cameras such as the Cylindrograph, Wonder Panoramic, Pantascopic and Cyclo-Pan, are some examples of panoramic cameras.
                
                
View from the top of Lookout Mountain, Tennessee, Albumen prints, February, 1864, by George N. Barnard
                
                
Center City Philadelphia panorama, from 1913.
In the 1970s and 1980s, a school of art photographers took up panoramic photography, inventing new cameras and using found and updated antique cameras to revive the format. The new panoramists included Kenneth Snelson, David Avison, Art Sinsabaugh, and Jim Alinder.
Panoramic cameras and methods
                
                
A 1900 advertisement for a short rotation panoramic camera
Short rotation, rotating lens and swing lens cameras have a lens that rotates around the camera's rear nodal point and use a curved film plane. As the photograph is taken, the lens pivots around its nodal point while a slit exposes a vertical strip of film that is aligned with the axis of the lens. The exposure usually takes a fraction of a second. Typically, these cameras capture a field of view between 110° to 140° and an aspect ratio of 2:1 to 4:1. The images produced occupy between 1.5 and 3 times as much space on the negative as the standard 24 mm x 36 mm 35 mm frame.
Cameras of this type include the Widelux, Noblex, and the Horizon. These have a negative size of approximately 24x58 mm. The Russian "Spaceview FT-2", originally an artillery spotting camera, produced wider negatives, 12 exposures on a 36-exposure 35 mm film.
                
                
A negative from a 35 mm swing lens camera
Short rotation cameras usually offer few shutter speeds and have poor focusing ability. Most models have a fixed focus lens, set to the hyperfocal distance of the maximum aperture of the lens, often at around 10 meters (30 ft). Photographers wishing to photograph closer subjects must use a small aperture to bring the foreground into focus, limiting the camera's use in low-light situations.
                
                
The distortion of architectural subjects is severe when using a rotating lens camera
Rotating lens cameras produce distortion of straight lines. This looks unusual because the image, which was captured from a sweeping, curved perspective, is being viewed flat. To view the image correctly, the viewer would have to produce a sufficiently large print and curve it identically to the curve of the film plane. This distortion can be reduced by using a swing-lens camera with a standard focal length lens. The FT-2 has a 50 mm while most other 35 mm swing lens cameras use a wide-angle lens, often 28 mm].[citation needed]
Full rotation
                
                
360-degree panoramic projection of the VLT survey telescope.
Rotating panoramic cameras, also called slit scan or scanning cameras are capable of 360° or greater degree of rotation. A clockwork or motorized mechanism rotates the camera continuously and pulls the film through the camera, so the motion of the film matches that of the image movement across the image plane. Exposure is made through a narrow slit. The central part of the image field produces a very sharp picture that is consistent across the frame.
Digital rotating line cameras image a 360° panorama line by line. The camera's linear sensor has 10,000 CCD elements. Digital cameras in this style are the Panoscan and Eyescan. Analogue cameras include the Cirkut, Hulcherama, Leme, Roundshot and Globuscope. There are also add-on panoramic video lenses for smartphones such as the Go Pano micro and Kogeto Dot.
Fixed lens
Fixed lens cameras, also called flatback, wide view or wide field, have fixed lenses and a flat image plane. These are the most common form of panoramic camera and range from inexpensive APS cameras to sophisticated 6x17 cm and 6x24 cm medium format cameras. Panoramic cameras using sheet film are available in formats up to 10x24 inches. APS or 35 mm cameras produce cropped images in a panoramic aspect ratio using a small area of film. Advanced 35 mm or medium format fixed-lens panoramic cameras use the full height of the film and produce images with a greater image width than normal.
Because they expose the film in a single exposure, fixed lens cameras can be used with electronic flash, which would not work consistently with rotational panoramic cameras.
With a flat image plane, 90° is the widest field of view that can be captured in focus and without significant wide-angle distortion or vignetting. Lenses with an imaging angle approaching 120 degrees require a center filter to correct vignetting at the edges of the image. Lenses that capture angles of up to 180°, commonly known as fisheye lenses exhibit extreme geometrical distortion but typically display less brightness falloff than rectilinearlenses.
Examples of this type of camera are: Hasselblad X-Pan (35 mm), Linhof 612PC, Horseman SW612, Linhof Technorama 617, Tomiyama Art Panorama 617 and 624, and Fuji G617 and GX617 (Medium format (film)).
The panomorph lens provides a full hemispheric field of view with no blind spot, unlike catadioptric lenses.
Segmented
                
                
Example of a segmented panorama. Taken with a Nikon Coolpix 5000 and stitched with PTgui.
Segmented panoramas, also called stitched panoramas, are made by joining multiple photographs with slightly overlapping fields of view to create a panoramic image. Stitching software is used to combine multiple images. In order to correctly stitch images together without parallax error, the camera must be rotated about the center of its entrance pupil.[2][4][5] Some digital cameras can do the stitching internally, either as a standard feature or by installing a smartphone app.
                
                
Upper Falls on the Genesee River, downtown Rochester, New York. Taken with a Sony A700. 2 rows of 5 images per row, stitched as a mosaic using PTGui.
                
                
The Giza Pyramids in Cairo, Egypt
Catadioptric cameras
Lens and mirror based (catadioptric) cameras consist of lenses and curved mirrors that reflect a 360 degree field of view into the lens' optics. The mirror shape and lens used are specifically chosen and arranged so that the camera maintains a single viewpoint. The single viewpoint means the complete panorama is effectively imaged or viewed from a single point in space. One can simply warp the acquired image into a cylindrical or spherical panorama. Even perspective views of smaller fields of view can be accurately computed.
The biggest advantage of catadioptric systems is that because one uses mirrors to bend the light rays instead of lenses (like fish eye), the image has almost no chromatic aberrations or distortions. Because the complete panorama is imaged at once, dynamic scenes can be captured without problems. Panoramic video can be captured and has found applications in robotics and journalism.
                
                
A panoramic photograph of the Camp Nou stadium, Barcelona in January 2011
Built-in digicam feature
                
                
Pandu Parrochial Church, Bandung, taken with Samsung Monte Camera
Panoramic photography is built into some digital cameras, using firmware to capture and stitich multiple images. Even some low-end cameras include this capability:
2 to 3 shots overlapping stich panorama by Fujifilm FinePix S1800
sweep (motion) panorama by Fujifilm Finepix S4000
3D sweep panorama by Sony Cyber-Shot DSC-HX9V; also in some of the latest Sony Ericsson smartphones in the Xperia series