Landscape and Panoramic Photography.
Have you ever wished to record a scene that just cannot be covered by a wide angle lens. That's because you realise that using extreme wide angles will result in severe distortion of landscape views. Vertical lines, such as the edges of buildings, appear to curve and peoples heads are distorted out of shape. To achieve a true panoramic landscape what you really require is a lens that swings through an arc - rather like the way it happens in life when turning your head.
The advantage of revolving the lens is that a very wide angle of view can be shot. Typically 120 to 140 degrees of angle. A fixed lens camera can only record without distortion about 90 degrees. And those lenses require expensive graduated central spot filters to compensate for the of axis fall off. These swing lens cameras record only a central slit as the lens revolves and so therefore only the centre of the lens records the image. This means that the centre of the image is as sharp as the edge.
Some cameras use a narrower strip of film but the same length as normal to achieve the wide affect. This includes some of the cheaper 35mm SLR's, 35mm compacts, and Digital Cameras with the panoramic options. Other cameras use a lens that covers a wider format of film than usual and then place a longer strip of film behind it. But the latter is not really TRUE panorama, but a chopped off - top and bottom - wide angle shot
With all these cameras the widest angle of view is 90 degrees. And the major problem is that the lenses must be large and of extremely high quality so that the edges of the image are as sharp as the centre. These lenses make the cameras very expensive.