Figure 5-2. Dissociation of planes in oblique views (after Tillier). When the incident radiation is in the direction of arrow 1, the images of parts A, B, C, and D of the object are projected in the order c, a, d, b on the film. With incident radiation in the direction of arrow 2, however, the order is a, c, b, d. Thus when the tube is displaced to the right, the upper plane (AB) becomes displaced to the left in relation to the lower plane (CD). Click for high resolution image.