Page 29 - Loss of the VOC Retourschip Batavia, Western Australia, 1629

Figure 17. Tagging the hull timben prior to photography and raising.
tanks. During bad weather periods, the timbers were removed from the tanks, drawn, photographed again (see below), and then wrapped in polythene tubing for storage.
The drawings of the timbers were made by tracing the surface shape and features directly onto thin-gauge, poly- thene sheeting. There were several major drawbacks to this system. Due to the opaqueness of the sheeting, it was hard to trace surface features. As weIl, irregularities such as concretion caused distortions in the tracing. The tracing had to be done outside and, as a result, wind also caused problems. There was a danger that the tracing sheet could slip on the timber without being noticed, thus causing errors.Oftentheheatofthesuncausedcondensationonthe inside of the sheeting, obscuring the underlying timber. With care and patience, most of these problems could be overcome, but the bulk of these drawings needed to be supplemented by photographs. It would have been more useful to trace on clear regular film, but the cost involved was prohibitive. The speed with which the timbers could be recorded was a major factor in favour of the system. Furthermore, the need here for recording information immediately after raising cannot be over emphasized. Not only was there a danger that the timber might warp or crack, but also there was a risk of unavoidable damage during the lengthy handling process of their 500 km trip to
the Conservation Laboratory.
Underwater photographic recording
All underwater record photographs were taken with a
standard 35 mm Nikonos camera, fitted with either the 28 mm or 15 mm Nikanos water-corrected lenses. This camera system is perfectly suited far work such as this, as it is compact, rugged, and produces exceIlent distortion-free results. Initially, during the fust two seasons, the 28 mm lenses were used, but subsequently these were replaced with the superior 15 mm lens. The effective focal lengths of the lenses, in water,are 37.5 mm for the 28 mm lens and 20 mm for the 15 mm lens, giving angular views of 51° x 35° and 84° x 62° respectively. The 28 mm lens needs almost twice thecamera-subject distance to cover the same area as the 15 mm lens, and as a result, the quality and sharpness of photographs taken with the 28 mm lens tended to be poor when compared with photographs taken of the same subject with the 15 mm lens. AIl underwater record photographs were taken on Ilford FP4 film rated at 125ASA and developed in the normal way with a fme- grain developer. The normal exposure range for the wreck site was F/4 to F/8 at 1/125 sec. 'Three types of photo- graphic recording were carried out on this site: site photo- mosaic, timber photomosaic, and stereo-recording.
A phatomosaic o f the whole wreck site was made at the start of the fust season, to supplement the site plan. The ground control consisted of seven taut paraIlellines 1 m apart and 46 m long, laid along the long axis of the wreck
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