PHOTOGRAPHIC LIGHT SOURCES 



289 



Reflectors. — The light produced from Hght sources may frequently be used much 

 more effectively if a reflector is used with it. The reflector does not produce any 

 more light than is generated by the light source, but directs it to the desired position 

 where it may be used more advantageously. Reflectors may be used at the light 

 source, in which case they are most efficient, or may be used near the subject being 

 photographed, where their use gives flexible control over modeling and light contrast. 

 Where sharp shadows are desired or are at least not objectionable, smooth, polished 

 reflectors of the specular type may be used, but where "soft" diffused lighting is 

 desired, etched, hammered, or diffuse reflectors are more suitable. The degree of 



rX- 



Plane Re-Flec+or 



Conicoil Ref lec+or 



Fig. 



Spherical Ref lec+or Paroiboloicl Ref lec+or 



Loimp 01+ Focus Lamp a+ Focus 



Ina'deni ra\/s Re flecied rays 



19. — Incident and reflected rays for various shapes of specular reflectors, showing 

 approximately how the reflected beams are spread. 



diffusion may be increased by placing diffusion screens of tissue paper, linen tracing 

 paper, ground glass, opal glass, or similar material in the path of the light rays. 



The effectiveness of a reflector used in conjunction with a light source depends 

 upon: (1) the shape of the reflector, (2) the material out of which the reflector is made, 

 and (3) the surface treatment of the reflector. Figure 19 shows a diagrammatic 

 representation of a light source used with polished specular reflectors of certain com- 

 mon forms, together with the net light beams produced. From this diagram it is 

 evident that the flat plane reflector is most suitable for producing a well-diffused 

 source, whereas the parabolic reflector produces a sharply defined beam. Other 

 forms of reflectors shown produce intermediate effects between these two extremes. 



The material out of which the reflector is made as well as the polish of the surface 

 determine the amount of incident light which is reflected from its surface. Table IX 



