Page 357 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

336 Maritime Archaeology: A Technical Handbook, Second Edition
Figure 12.5 Westerwaldware jug with the scale placed in the plane of the outline so that the profile can be measured.
on the surface of the object. By observing through the viewfinder the reflec- tion of the front of the lens in the mirror, the camera can be adjusted on the tripod so that the image is symmetrical in the viewfinder (Figure 12.6). This is a very easy and convenient method of leveling a camera, particu- larly when the focusing screen has a cross wire or central circle engraved on it. It is also very useful for leveling the camera when copying plans and documents where the camera also has to be accurately level.
The scale in the photograph is thus placed in such a way that the scale plane lies either in the plane of the outline of the object or in the plane of the detail. It is obvious that in some cases it may be necessary to place two scales or to take several photographs with the scales in different positions.
Various types of scales can be used for photographic purposes. For fine scales, millimeter graduations of the edge of a white scale rule can be used. Larger centimeter scales are most conveniently produced by computer graphics (Figure 12.7). To do this, first draw the scale, for example, a 200- mm long checker board (black and white with 10-mm graduations), which can be printed on transparent drafting filmthe printed result is a cheap, handy, waterproof scale that has a variety of uses. Glued onto plastic, it forms a rigid strip scale, or mounted on a wooden block, it can be used as a stand-up scale. For larger scales, one can use a 1-m rule painted black and white at 100-mm intervals or, alternatively, plastic or aluminum round or square section tubing. It is recommended that the size of the graduations