372 



ERECT IMAGES IN DRAWINGS 



ICn. X 



(3) The use of a prism or of a mirror to change the direction of the rays on 

 their way to the screen (fig. 192). 



(4) The use of an opaque screen. 



(5) The use of a translucent screen. 



appear erect like fig. 211 when seen through the translucent screen 

 and facing the light. 



Facing the light, the object on the stage will also appear erect. 



POSITION OF THE OBJECT FOR AN ERECT IMAGE WITH AN OBJECTIVE 



AND OCULAR, AND A 45 DEGREE MIRROR OR A TOTALLY 



REFLECTING PRISM 



524. For an opaque horizontal screen. (A) For the draw- 

 ing table and mirror (fig. 182), place the object on the stage so that 

 it faces the objective and is with the lower edge up. The image will 

 appear erect on the drawing surface when the observer faces away 

 from the light. 



FIG. 215. EARLY METHODS OF DRAWING WITH PROJECTION APPARATUS. 



In the picture at the left (Fig. 6) is shown a drawing tent or box with a 45 

 mirror and vertical objective by which an erect image is projected upon the 

 drawing table as in figures 88-89. The artist sits outside, but has his head 

 and bust within and the light is excluded by a cloth curtain over the back. 



In Fig. 5 is shown a drawing box composed of an objective at the right (CD), 

 a 45 mirror (E F), and a drawing surface (C) covered by a sloping roof of 

 opaque material to keep out the light. With this instrument the artist simply 

 introduces the hand and pencil. The picture will have the rights and lefts 

 reversed as the drawing is made on the back of the drawing paper, not on the 

 front as with Fig. 6. 



Fig. 4 is to show the course of the rays from an object (A B), and its inverted 

 image (G H). When the mirror (E F) is introduced the image (/ K) is rendered 

 horizontal. 



