Panoramas

Many people are familiar with photographic panoramas as a means of producing a wider view of a scene than their camera allows. Multiple images are ‘stitched’ together, either manually or using software designed for the task and an extended image is produced.

The technique, in its simplest form, provides a couple of advantages. Firstly, a wide ange view is produced without the need to buy a special lens to take the picture in one shot and, secondly, the panorama produced has many more pixels than a single shot would have produced so is often more detailed than a single shot.

The secret of taking a panorama which fits together easily is to take all the separate shots rotating the camera around what is commonly called the ‘nodal point’ of the lens. This point is that at which rotation of the lens produces no parallax errors in the images. Although it is not difficult to produce acceptable panoramas hand-held, it is more successful when the camera is mounted on a tripod and uses a special mount which allows accurate rotation around the nodal point. Defining this point for a particular lens is adequately described elsewhere.

Stitching software can cope easily enough with images with varying slope, pan and rotation but will not produce the best posible matches when the images show parallax differences - the nodal point mount addresses this problem.

On this site there are several examples of simple panoramas but many are rather more. Taken to its logical conclusion a panorama can be made to show a whole scene, front and back, up and down, from the point-of-view of the observer. Such panoramas are often described as being 360° panoramas and require, not only special software to produce them, but also special software to view them.

The process begins with the photographic process. A full 360° view can be produced with any camera and lens combination but normally a wide-angle lens would be used. Most of the panos on this site have been produced with an 8mm fisheye lens which allows a full view to be produced in four images (theorectically it could be done in 2 images as the lens can produce a 180° by180° view but it is helpful to have a good overlap of the images).

Exposure control while using extreme wide angle lenses lenses is potentially difficult, theory would dictate that one should correctly expose the brightest of the four views and use the same exposure and white balance settings for the other images. The stitching software has to deal with a large range of contrasts but the better programs are written to do this.

Another method of exposure control is to use the HDR photographic method. Once again, this is well described elsewhere but it is worth noting that the top software can handle HDR imaging.

If the four images have been well taken then the stitching program should be able to assess how best to arrange the images automatically and output the panoramic image with little effort.

The 360° images used on this site are in Adobe’s Flash (.swf) format. This has been chosen as it seems to be compatible with more browsers than Quicktime (.mov) files although currently 64-bit browsers have no fully functional Flash plug-in. At th time of writing Adobe has beta versions available but these appear not yet to be fully functional.