The purpose for which the swing back is employed in portraiture is just the opposite to that for which it is used in architectural work. In the former it is used to accommodate the focus to a figure that does not present a plane surface to the camera. The result is a certain amount of distortion in the Sgure, but the defect is scarcely apparent unless overdone, and is compensated for by shortening the time of exposure and improved definition. Cameras for portraiture and for architectural work should have swing backs capable of an outward and an inward swing. For this reason the reversing frame must swing from the centre, or the side stays must be specially constructed to lift the travelling frame out of the way of the base. Most field cameras are made to swing forward only. When photographing a sitting figure (represented by the hatched lines in the illustration), it will be seen that the knees are much nearer the camera than the head; therefore, either a much smaller stop must be used, thus greatly increasing the time of exposure, or the swing back of the camera must be altered as shown in the illustration, so that the plate may repeat the plane of focus as in dicated by the dotted lines A B.

Use of Swing Back in Portraiture.