The Camera Obscura.

Above the town of Aberystwyth on Constitution Hill can be found a restored Victorian building which houses what is known as a Camera Obscura. Back at the turn of the century Mid -Wales was the focal point of all leisure activities. The cliff railway ferried people to the 430ft summit where a host of amusements such as a bandstand, a glittering ballroom, tearooms, a switchback railway and a Camera Obscura were situated.

The “Luna Park” as it was then known, was the nearest the Victorians got to a 20th century theme park. The new Great Aberystwyth Camera was designed to be sympathetic to its Victorian heritage, with wide viewing balconies and an overhanging roof. The two-story octagonal tower is based on the dimensions of the original Constitution Hill Camera Obscura, and the foundations for the original building can be seen next to the Camera Obscura.

A substantial structure was needed both to support nearly half a ton of optics in the centre of the roof, and to withstand winter gales of up to 100mph at the exposed location at the top of the 430ft cliff. There was no road access to this spot and during the Camera Obscura’s construction, materials and equipment had to be brought across grassy tracks only yards away from the cliff edge.

The Camera Obscura was designed with an enormous 3 element lens that is precision ground to give an image of incredible clarity and detail. The huge 14 inch lens was designed and manufactured in Wales by Pilkington PE Ltd of St Asaph, Clwyd. The total weight of the mirror and lens assemblies is more than 1000 lbs.

The f20 lens has a 10 degree field of vision and a focal length of 6.4 metres. An indication of the accuracy with which this lens system has been made is that the face of one of the lens elements has been ground to a radius of 5km. The lens remains fixed to the building, while the mirror above the lens is motorised so that it can be rotated through most of the 360 degree panorama. It can also be tilted to take in near objects as well as the horizon. Control of this massive instrument is maintained by using a joystick next to the viewing screen. The custom made screen table is 52 inches in diameter and like almost every other part of the project was designed and manufactured in Wales.

Moving the lens into position was a major operation. Special lifting equipment was built into the steel frame of the building during construction, and a dummy lens was used in practice to ensure that the lifting of the real, and very expensive, lens went without a hitch. The lift equipment is retained to allow the lens to be removed for cleaning and adjustment.

The new Aberystwyth Camera Obscura was opened in 1985. Its massive 14inch lens makes it not only the biggest Camera Obscura in the world, but also allows a bird’s eye view of more than 1000 square miles of sea and scenery. The apparatus inside the Camera Obscura works by using a mirror placed at the top of the building to reflect the view through the lens, which focuses the image onto a circular screen in the darkened room below. The simplest form of Camera Obscura (which means “darkened room” in latin) has been in use 2000 years. A completely darkened room with just one small hole in one wall will produce an image on the wall opposite the hole.

The image on the wall will be an inverted picture of what can be seen by looking through the hole. The bigger the hole, the brighter but more unfocused the image.

A pin hole camera works in exactly the same way. This simple apparatus can be improved by placing a lens in the hole to sharpen the image, and by using a mirror to correct the image reversal. The clarity of the image then depends on the quality of the lens and mirror.