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HANDBOOK OF PHOTOGRAPHY 



The fallacy of a totally fiat light can be best seen by an extremely elementary 

 example. Assume a red cube placed on a white cardboard. The camera lens looks 

 at the cube at 45°. If the cube is illuminated by a uniform light all around, the 

 finished picture will appear as in Fig. 6 which, although it shows a red object on a 

 white background, does not give the faintest indication of the actual shape of the red 

 object. Illuminate now the red cube with a single light source at an oblique angle. 

 The results will now be as in Fig. 7. 



Evidently proper lighting is giving perspective, and it shows correctly the geo- 

 metrical shape of the object. Color in this case adds the additional information of a 

 red cube onto a white background. 



To be of real practical value, color photography must be made to extend the scope 

 of black-and-white photography. 



Since the filter factors vary considerably with the type of light, it is not permissible 

 to mix lights of different types. If it is necessary to diffuse the source of light, this 

 should be done with wire gauze or any diffusing device which does not introduce any 

 change in the color value of the light. For the same reasons discolored reflectors 

 should also be avoided. 



The light source should also be steady. Daylight, incandescent, and photoflood 

 are all equally satisfactory. Each type obviously requires different filter factors. 



Fig. 6.— Cube illu- 

 minated by flat lighting 

 fails to show tone 

 gradations. 



Fig. 7.— Cube Ughted 

 obliquely. Several tones 

 are present. 



The best method of measurement consists in reading with a photometer the light 

 reflected by a white card placed directly over the high lights of the subject. This 

 exposure should be shghtly below the overexposure mark. Exposure meters, such 

 as Weston, carry this information. 



Flash bulbs also can be used satisfactorily, but great experience is necessary. It is 

 advisable to arrange the lighting and composition first by means of incandescent bulbs 

 placed in proximity with flash bulbs. Just before the firing of the flashes the incan- 

 descent lights can be turned off. 



It is not always possible to identify the three color-separation negatives and in 

 order to avoid errors three patches of colors corresponding to three filters or, if desired, 

 to three complementary printing colors should be placed along side the neutral-gray 

 wedge. 



When the gray wedge and color patches are properly illuminated to correspond 

 approximately to the high light of the subject, they will serve several purposes; i.e., 

 identification of the negatives, measurement of contrast, and measurement of printing 

 ratio. The identification of the negatives can be obtained also by suitable marks 

 along the edges of the holders or of the filters in close contact with the emulsion, and 

 the contrast of development can be assured by standardizing time and temperature. 

 However, the possibility of being able to measure the printing ratio is a convenience 



