The photographic plate: Spectral sensitivity
 
Photographic emulsions are available for the whole of the optical spectrum except the infrared region beyond 12 000 A^˚ . The basic sensitivity of the silver bromide runs from beyond the ultraviolet to about 5000 ˚A but, by adding various dyes to the emulsion, the spectral coverage can be improved. The relative spectral sensitivities of the major classes of emulsion types are illustrated in figure 1.

Figure 1. Relative spectral sensitivity of typical unsensitized, orthochromatic, panchromatic and infrared (IN and IZ) emulsions.