As good as digital SLR cameras are, they do have a significant drawback - a set and limited resolution. With film cameras, even 35mm, the size you can print an image is only restricted by the enlarger you are working with. As the image size increases, the size of the grain increases, but the image quality does not rapidly deteriorate. With a digital camera, however, there is only a fixed amount of resources (resolution) to be enlarged, and when this resource is exceeded, the image quality drops rapidly. Technology will improve (endlessly so, it would appear) and higher resolution cameras will be developed but for the moment the only way to overcome the limited resolution of a digital camera is to put together multiple images to create higher-resolution files to print from.
My approach to stitching is fairly basic - I set the camera up on the tripod, try to keep it level and begin making overlapping images. For the sample image here of Ingrid, I made eight frames, which were assembled together to produce an image more then three times larger then the actual resolution of the 6mp camera - the final print will print 10"x22” without any interpolation - this from a camera that produced a 7"x10” print at highest quality. Add to this work flow the ability to interpolate an image up to twice as large, and this approach yields an image that can print 20"x44” in size - about 1/2 life sized! Stitching has permitted me to make files that print as large as 80” high directly from the camera image, and with files sized that top 350 million pixels in resolution!
There are issues that arrive with this approach; first, because I am simply rotating the camera through the composition, there are problems with perspective - as the camera is moved, the relationship between objects changes (like switching between one eye and the other, while looking out a window - you can see slightly different scenes from each eye, even though they are only separated by four inches). I overcome this by selective editing in the reassembling but there are other solutions.
Several companies make VR (Virtual Reality) tripod heads which rotate the camera around the center of the lens (known as the nodal point). In the fall of 2004, I bought a variation on this solution, a Nodal Ninja. This tool works well for what it is designed for, and while I do not use it for every session, I do bring it into play occasionally when I am making a large number of stitched images.
There are two kinds of stitching, one for a wider-angle, and one for resolution.