Methods & Aims in Archaeology

by W. M. Flinders Petrie

Reflectors are also very useful for lighting dark subjects. Three or four sheets of tin plate should have the edges turned up to stiffen them, and be of slightly different sizes so as to nest together for carrying. One planted in the sunshine outside a tomb will send a beam in, which may be reflected again by another. With three successive reflections, round two right angles, I have lighted an entirely dark chamber ([Fig. 45]) enough to photograph with five minutes exposure and full aperture. The successive reflections so neutralise each other’s variations that a very uniform lighting results.

If a flat surface with different colour is the object, then a light exactly from behind the camera is best, so as to avoid any shadows. A faint ink-writing on rough pottery will appear with a back light when it seems quite hopeless in a side light. For papyri two equal electric arc lights are placed, one on each side of the camera, so that there can be no shadows and no reflections.

Arrangement of objects.

Backgrounds should be considered. For most objects there is nothing so good as black velvet, as a long exposure can be taken so as to bring out the shadows on the object, without any glare from the background. The ground should extend far beyond the object, as any bright surface near the object may make internal reflections in the camera. In short, no bright surface should be visible within 60° of the axis of the lens. For dark objects of which the outline alone is important a light ground might be used; though even here probably a black ground and long exposure would be better. A glass background with light or dark surface some distance behind it is used sometimes, so as to avoid all shadows from objects. But in many cases a shadow is positively useful, and adds to the intelligibility of the view.

The direction of the camera is too often horizontal. For portable objects a vertical position is generally better, and for groups it is essential ([Fig. 46]). The background on which the objects are laid can be tilted so as to get oblique light from sun or window, and the camera tilted equally from the vertical by shifting the legs. Scraps of wax can be stuck on below objects, so as to keep them in any exact position required for lighting or viewing, or scraps of charcoal used as wedges which do not show on the black backing. There is no need to trouble about depth of focus, as the insertion of a small stop, as f/100, is enough to bring up every part sharp. I have taken a bracelet ([Fig. 47]) with the sides at 7 and 9 inches from the lens both in perfectly sharp focus. In fact, a subject may be contracted into the plate by putting it out of focus, and then focussed by the stop. For all cases of large-scale photographs or enlargements it is best to focus by shifting the distance from object to lens, and not from lens to plate.

Fig. 46. Foundation deposit, laid out horizontally.

Fig. 47. Bracelet of King Zer, 7 and 9 ins. from lens.

In setting up the camera everything should be done as far as possible before looking into it,—the distance measured for the scale required, the camera set square with the plane of the object in both directions, and set so as to have the object upright on the plate. All of this can be far better dealt with from outside. The actual focussing and slight adjustments can then be done when viewing the ground glass. For skew positions it is best to hold the camera in the hand where it ought to be, keeping the legs turned up from the ground; and then drop the legs one after another, so as to touch the ground or some object; thus the camera will be left standing in the required position. The stand should not have the legs packed by folding sideways; but they should be capable of being shortened to the single length while fixed to the camera, as it is often needful to support it only a foot from the ground. A stand should be so made as to give the greatest range of height. A common fault of beginners is not covering the plate, but letting the image be smaller than necessary. Unless working to some uniform scale, an object should be shown as large as the plate allows; always remembering that a lantern slide will seldom take more than 3 inches diameter, and hardly a full 3 inches square. It is convenient to fill a ¼ plate with a group, of which the least important objects are at the sides, and so can be omitted in a lantern-slide print. A most troublesome matter is taking a series of wall scenes so that they will fit exactly together at the edges. Probably it pays best to do them approximately in the field, and then enlarge in a copying camera on to a ruled ground, and so remove all irregularities of scale and of skewness. For working to a uniform scale it is best to fix it by keeping the focal length unchanged and measuring the distance of the camera from the object, and not to refer to the size on the glass.