ENLARGING AND COPYING.
Tt has been stated that a pinhole may be used for copying and enlarging, and for such work the smallest pinhole, about of an inch, should be used, and the focus considered as some round number, which may, for convenience sake. be taken as the nearest whole number less than the longer side of the plate we use ; thus, 4 in. for a quarter-plate, 6 in. for a half-plate, and so on. The convenience of this is obvious when we come to use the following table, which gives the relative distances between . pinhole and subject. and pinhole and plate, when enlarging, reducing, or copying. If one uses a box with a fixed distance, say O or 8 in., then one must reckon the dis tance to place the camera from the picture or subject to be copied, and this is very easy ; for instance, suppose we determine on 6 in. as the plate distance for a half plate, and we want to copy a picture in. long ; well, allowing for margins, we should reduce this to 6 in., or one-fourth—
therefore, the distance between the picture and pinhole should be four times our plate distance, or 24 in. The rule, therefore, is very simple : multiply the fixed plate dis tance by as many times as you reduce the size of the object, and the result will he the distance between pinhole and subject. For a variable or focussing camera, use or inch aperture and consider that the true focus is as stated above, then the an nexed table will give the relative distances for enlarging and reducing, or copying. Not much explanation is wanted of these figures. as each column is explained by the words above or below. The numbers are but ratios, and if the focus of the pinhole is fixed at a given distance, then this mast be multiplied by the figures in the tables to obtain the necessary enlargement or reduction.