Joining together panorama pictures
Even if a photo is limited to length and width it can still open your eyes to a three-dimensional space. Even in a large formal panorama photo the eye can wander freely. On the screen, however, the possibilities can be extended endlessly. It is possible to jump through rooms at the click of the mouse, take an interactive tour through a building and choose the viewpoint freely.
This kind of all-round view is no longer stuck together from numerous individual pictures - the job is now done by specialised software. Usually one only has to feed in suitable picture material and the so-called 'stitching' is done independently. This is why the picture material should be of high quality.
This section shows how to create a perfect panoramic picture.
Preparations
In order to create a series of images you need the secure basis of a tripod. Some models are even fitted with scales on the angled joints of the tripod head. They help to capture the image in equal sections. Some software does work smoothly even if the panorama view is taken using a hand-held camera. But some are grateful to the revolving angle in order to mount more precisely.
You should also use a remote exposure cable. Manual operation causes shaking, especially on longer exposure times, and can even move the tripod.
Objects in the foreground and background retain the same
horizontal distance by revolving around the nodal point.
If you turn on your own axis this causes a parallax shift - objects in the background appear to alter their distance to those in the foreground. In order to avoid this you should revolve around a nodal point instead - an imaginary point approximately in or in front of the lens. It depends on the focal length of image and must be calculated individually if not provided by the lens manufacturer.
We recommend you purchase a nodal point adaptor for your tripod in order to substantially simplify the circle motion. The shift can also be avoided by selecting a scene with an empty foreground and taking images of scenery that is further away.
Wide angle lenses with a short focal length are recommended to capture a large image field. In this way the stitched panorama does not turn out as a narrow strip but rather the sky and ground provide the image with sufficient space.
The dimensions of the image filed depend on the diagonal of the sensor and the focal length (more precisely the image width that is equal to the focal length with the distance setting on 'infinity'). In order to formulate this as a number it is given as an image angle in degrees. As the Horizontal Field Of View (HFOV) is demanded by some software in order to make an exact image calculation. In order to do the calculation we suggest you refer to the Website of Brian Chandler. You need only input the focal length of the lens and the size of the APS-C sensor (23.7 x 15.6 mm).
Normally you will want to capture a landscape in perfect focus by selecting a high aperture number. It is not, however, always necessary to go the top end of the scale, which reduces the possible range for the shutter speed and amplifies undesirable movement effects.
Instead you should achieve the optimal depth of field with a somewhat lower aperture number. This requires the calculation of the hyper focal distance, i.e. the distance from the camera to the optimal focus point. Luckily this can be read off most interchangeable lenses, as shown on the right in the screen shot.
Setting the camera
- 1. The most important prerequisite is to fit the tripod and the camera with a spirit level. The camera should not be tipped forwards and should be absolutely horizontal. The tripod will only be tipped for sphere panoramas in order to include sky and ground. If you own a camera with a degree scale the panorama software can be set with a constant angle and the rotation angle.
- 2. If you do not know the hyper focal distance then you should probably select the largest aperture value and set the focus to infinity to capture the entire space in focus.
- 3. Automatic settings lead to unpredictable results. For this reason you should not allow the camera to make its own settings, especially for white balance, but rather set them yourself.
- 4. A clear day around noon is particularly well suited for outdoor pictures. At this time the shadows will not fall in different directions across the picture and the space is often more evenly lit.
- 5. The change from light fields and dark avenues still, however, leads to abrupt changes in brightness. They could be equalized with a faster or slower shutter speed. However the lighting equalization could lead to slight under- or overexposure.
- 6. The optional grid network in the display of an Epson R-D1s creates additional fixed orientation points. They are particularly important when the tripod does not have a degree scale. Panorama programmes need overlapping photos so that no seams or ghost images can be seen after the montage.
Software can stitch precisely if the angles of rotation and inclination are known.
Software requirements
Good panorama software programmes are multi-talented. They don't just join the total picture but also remove all picture faults. They correct distortions, particularly in wide-angle lenses, equalize the colour and brightness of individual photos and ensure inconspicuous blending.
User interface of the Ptgui programme.
Your output is very important, in particular if the panorama is to be viewed on the Internet. The file format sets later possibilities and limits. In the Virtual Reality Modeling Language (VRML) a picture could be projected artificially on to the inside of a sphere and allowed to rotate on the monitor. It is, however, quite difficult to wander around in these worlds as they have relatively long download times. The extended Standard Extensible 3D (X3D) has replaced VRML.
Studies are not necessary to explore all the possibilities of the programming language Java. Fortunately some software produces the relevant files for a three-dimensional view on the screen together with the panorama.
The so-called Image Based Rendering, as seen in the image viewer "QuickTime VR", has become a kind of standard. This involves packing the panorama image into a file with the ending .mov. Usually you can then pick various viewpoints, zoom on to details and of course freely select perspective.