THE FISH EYE VIEW OF THE CITY OF LONDON
An enigmatic circular engraving of the view from St Pauls’ Golden Gallery
A POSSIBLE FISH EYE VIEWING CABINET
[Note: the illustrations to be added]
In The Map Collector for June 1987 Ralph Hyde of the City of London Guildhall Library described an anonymous and undated circular view of the City -
Only three examples are known, but Ralph Hyde convincingly argued that the Fisheye View was derived about 1845 from the lost cylindrical painting by Thomas Horner, exhibited in the Colosseum in Regents Park in 1829-
The article went on to point out that the Fisheye View was in fact a particular type of a previously known construction, the anamorph. This is a perspective which uses a picture plane not at right angles to the direction of view, and which may be curved. The result is that a correct reconstruction can only be obtained from a single viewing position, sometimes reflecting the image in a mirror, flat or curved; from any other position the picture appears grossly distorted and in most cases unrecognisable. They enjoyed a minor popularity as puzzle pictures or for pornography and treasonable portraits. The National Gallery has just cleaned and re-
The one question left open was what the Fisheye View was for. It is rather large and cumbersome, difficult to look at as it requires turning constantly and would be ruined by being folded -
The first thing to strike one is the size of the central blank area, much too large for a conventional cylindrical mirror anamorph -
Looking down, assuming one's close-
What is unexpected is that this distortion is not significant over a small area when viewed from the centre of the View in the manner suggested. This is because if, in real life, one looks downwards all verticals converge to a point directly below one's feet -
Figure 1 demonstrates this effect on a simple cube. Viewed normally it appears wedge shaped and elongated, with the verticals converging to a point just above the bottom edge of the paper -
That this works for the Fisheye View is completely fortuitous, but may have been the only method of viewing envisaged; it is certainly very easy, if looking a little ridiculous -
More interesting is to devise a method of reconstrucing a true 360 degree panorama all round one, with the horizon truly horizontal, as suggested by Ralph Hyde. The View is not laterally inverted, so this would involve two mirrors, and a possible configuration is shown in section in Figure 3.
The horizontal line of view is turned through two 45 degree angles to drop vertically onto the horizon of the View. As the View is circular these two mirrors (angled much like a pentaprism in a single lens reflex camera) have to be curved round it to form truncated cones. The observer inserts his head from below through the central hole as before. Some method of lighting the View is neccessary, and a window in the angle between the two mirrors is suggested. This also has to be curved into a truncated cone.
The finished object is rather complex and difficult to constuct, nothing being rectangular, and the exact dimentions were arrived at by graphical trial and error. Accurate conical mirrors in particular are a substantial technical problem. It is thus open to question whether such a device could have been constucted at all by the producers of the Fisheye View, and it is certain it could not have been economically mass produced, as the mirrors would have had to be made from highly polished speculum metal. One could perhaps envisage a single example as an attraction in an optics gallery, much like Hoogstraten's Cabinet.
A rough half scale version has been constucted out of cardboard and mirrored Melinex plastic film to check that the effect is correct. The result, though not very good due to problems with the mirror fixings distorting the mirror, were sufficient to prove the principal. One problem could not be assessed, and that is the effect of binocular vision. Ideally the viewing position should be a single point (as in figure 1), and it is difficult to know if having two eyes either side the ideal point would produce a confusing effect in the full size version. The further back the viewing position is the less this is important, but the current design in fact puts the observer as far forward as possible in order to get the closest (and therefore largest) image and so that when the head is turned the axis of rotation is at the centre of the circle.
A full sized professionally constructed version would give a unique time-
However, without some forgotten attic disgorging a tarnished set of truncated cones, along perhaps with Horner's original working drawings, it is impossible to say if the Fisheye Viewer was ever originally constucted -
Copyright 1988. Roger Morgan is an Architect with an interest in anamorphs and perspective.