How it's done

The word panorama is used to describe any picture that captures a wide viewpoint - not necessarily a full 360-degree circular view. Single photographs are often referred to as "panoramic" if they are particularly wide - most APS cameras have a switch that enables panoramic mode.

It's also possible to produce panoramic pictures from a set of ordinarily-shaped photographs joined together. There's a range of equipment and software available that can do this "stitching" process automatically. Typically, these work along these lines: Any pattern that is recognised as appearing at the right hand side of photo A and at the left hand side of photo B will cause both photos to be stretched and squeezed until the patterns overlap completely.

The far edges are further away than the centre

One of the reasons why it's difficult to join photos together without distorting them is an effect of perspective. If you stand in front of a long building, for example, you will be closer to the part directly in front of you than to either of the edges.

When a photo is taken from this position, the edges of the building are likewise further from the camera than centre of the building is. Just as objects that are further away always appear smaller, this causes the building in the photograph to appear to shrink away gradually towards each edge:

The edges being further away result in the roof appearing to curve

This, of course, mirrors the way things appear to our eyes, and so doesn't usually look especially strange. However, it means that if two or more photographs are being joined together, it is going to be necessary to stretch and distort the pictures to get the edges to match.

A building photographed in three sections

360-degree panoramas are made by keeping the camera in the same spot but rotating it in a full circle, taking photographs at every angle. When these photographs are joined together, there emerges another effect of perspective in addition to the "shrinking edges" described above. Here's how it happens. Imagine a panoramic picture is being taken that includes the house in the diagram on the left. (To make things simpler, we'll concentrate just on this one thing in the picture, although the effect will be the same on everything that appears in the photographs.) As can be seen, the house features in three photographs.

Because the angle of each photograph is different, the house will appear at a different angle in each one. Photograph B is pretty much looking straight forward at the middle of the building. In photographs A and C, though, the house appears almost side-on because the viewer (and the camera) has turned to face a different angle. The result is three photographs as follows:

Three sections of the building, photographed from the same spot

When joined together, this produces an interesting effect in which the house appears to bend away from the viewer - again, with sides that are, on paper, much smaller than the middle.

The example was just of a single building across three photographs. This effect, though, will potentially be seen in every part of the picture if a full 360 degrees-worth of photos are used. At every point, buildings and streets that should be straight will appear to bend and shrink. Every large object will be a different shape and size in one photo from in the photo next to it. This is a major obstacle to producing one coherent and attractive picture.

There have been three main approaches to getting around the problem. The first approach does not even attempt to convert all this information into a flat picture: the panorama is presented as a three-dimensional animated image. The viewer can use a computer to change their viewpoint within the picture - and the sizes and shapes of things change to match that viewpoint. This gives a true impression of being surrounded by the picture, and can be fascinating to look at. The drawback, of course, is that the pictures can only be viewed on a computer.

The second approach is what happens in many software packages that automatically "stitch" photographs together. As described before, these work by bending and curving the lines in each photograph so that they match up with each other. The results can be really quite interesting, and it's possible to produce good pictures with quite inexpensive (or free) software and very little effort.

However, the bending and curving that this approach uses has the effect of making the panoramas seem rather unreal. To a greater or lesser extent, all horizontal lines (buildings, roads, paths etc) become curves, and the picture ceases to look like a real photograph. This isn't necessarily a bad thing, of course - it can sometimes be both striking and beautiful - but the presence of so many curves can detract from the realism of the picture.

My approach, therefore, does not use any automatic techniques. Each pair of photographs is carefully joined together using a computer art package, and every decision is made to ensure that the result looks as realistic as possible. I do this in various ways, including:

carefully choosing the places at which photographs are joined - for example, along the edges of buildings or kerbs
moving objects (e.g. people, cars, buildings, signposts, trees, walls) to fractionally different places, so that their positions are consistent with what appears on each side of the join
blending colours, patterns and textures (e.g. on lawns or roads) to make very gradual changes rather than sudden borders
painting in new branches, stones, lines and shapes to make other areas fit together

In these and many other ways, every alteration is made with the aim of producing a picture in which every area looks as though it is a direct record of what was really present. At the same time, I am able to make use of the perspective effects outlined above to the benefit of the picture - emphasising the dominance of some parts, and allowing straight buildings to appear to curve away from the eye.

The result is a set of pictures which our brains tell us can't possibly be accurate (because if a scene was continuously curving away from us then we couldn't possibly still see all of it) but which, simultaneously, appear to capture perfectly all of the details of a particular location. The results can be both bizarre and fascinating - I hope you enjoy them.

questions@panoramicyork.co.uk