Page 240 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 8: Field Photography 219
image sizes. Naturally these cameras are not (currently) underwater cameras, so a commercial housing has to be bought for it (or a custom housing built) to accommodate the camera. Recent experience with an Olympus Camedia 3000, with a custom-built housing, has demonstrated that this camera system, for archaeological work, now outweighs the Nikonos in ease of use, flexibility, and range of application. The small LCD monitor on the back of the camera can be used to frame pictures and is virtually an automatic one-control system. This digital camera system was used in 2001 at the Institute of Nautical Archaeology Tektash excava- tion in Turkey to carry out underwater survey work using photogrammetric software including PhotoModeler and stereophotogrammetry (see Chapter 6).
B. THE NIKONOS SYSTEM
Indisputably, the Nikonos camera is one of the most effective under- water cameras for archaeological work. The alternatives to the Nikonos range from the 120 format camera such as the Rollei Marine and Hasselblad, to the 35-mm single-lens reflex (SLR) camera. All of these are land cameras enclosed in custom-made watertight cases. The biggest problems under water with the 120 format are the limited depth of field and the restriction in the 12 frames available (although some cameras have 24 and 70 exposure backs). Generally, the system of placing a land camera in a watertight box has drawbacks. First, to load the camera it is usually necessary to remove it from the watertight case, and this involves disengaging a number of linkages and connectors. Often the person doing this is wet, so care has to be taken not to drip water into the case or camera. Secondly, the lens system on such cameras, although of good quality, is often impaired by the use of a plane port on the watertight case; this introduces a number of distortion effects. These effects can be remedied by using a specially designed domed port. Thirdly, the camera cases are usually bulky and relatively vulnerable; these shortcomings can create problems on a wreck site. Also, it is often thought that the advantage of using a camera housing is that one can utilize an exist- ing SLR camera, however, this can be a false economy. The housing is usually very expensive, especially when fitted with a correcting port. It can end up costing more than the complete Nikonos system with the expensive 15-mm lens (over US$1000). Additionally, the SLR camera will then be locked in a housing made unavailable for other terrestrial work. The main advantage of using an SLR camera in a case is the ability to frame photographs accurately and to deal with very close-up, or macro photography where precise focus- ing is essential.