i8o DRAWING BY THE AID OF PHOTOGRAPHY [Ch. VI 



screen must be used to get the desired size, which should be two, 

 three, or four times the size of the final picture. Use a large printing 

 frame, one 25 X 30 or 28 X 35 cm. (10 X 12 or 11 X 14 in.). Place 

 the printing frame, in which are a clear glass and a white sheet of 

 paper, against the wall or movable screen, and by moving the screen 

 or the apparatus get the picture the desired size. Now focus very 

 sharply. The diaphragm of the objective must be wide open. Turn 

 off the light from the arc lamp and place in the printing frame a 

 sheet of the photographic paper. Place a piece of ruby glass over the 

 end of the projection objective, turn on the light, and then arrange 

 the printing frame so that the picture is in the desired position. Re- 

 move the ruby glass and give an exposure of 2 to 5 seconds for the 

 arc hght or considerably more for a stereopticon mazda lamp. Re- 

 place the ruby glass over the objective, turn off the light, and develop 

 the picture as usual. A good plan to follow is to put a small piece 

 of paper in the printing frame and test the exposure before putting 

 the large sheet in the frame. The paper is too expensive to use the 

 large sheets for trial exposures. 



When the prints are developed, fixed and dried, the drawing in 

 lines is made as foUows: Use a drawing board with a piece of plane 

 glass in the middle (fig. 109) as the drawing shelf, and have under 

 it an incandescent lamp and metal reflector (fig. 109). Fix the print 

 face down on the drawing board and glass. The light from the 

 lamp shines through the paper and one can see the picture almost 

 as clearly as by looking at the face of the print. Now with the 

 T-square, etc., put in the lines desired. For a beginner it is best to 

 (io this with pencil. Then the pencil sketch can be inked in at any 

 time in the usual manner. While penciling in the Unes the light 

 should be turned off occasionally so that the pencil marks can be 

 seen clearly; then one can see whether any essential parts have been 

 omitted. The photographic paper is of excellent quality and takes 

 the right line pen almost as well as the best drawing paper. The 

 thick paper is used so that the photographic print will not show 

 through, and because the thick paper holds its form better than the 

 thinner paper. The thinner paper will also answer. 



One can use this method with blue prints also. It has the ad- 



