Liquid crystal cells can be used not only as an element of a display, but also as a part of other devices, for example fast optical shutter. In such a situation the response time of whole device depends not only of switching time of liquid crystal layer, but the mutual relation between optical matching of liquid crystal cell and spectral characteristic of light detector sensitivity also influences it. In this work the analysis of a switching time of whole device including thin twisted nematic cell (TN) and light detector with different Gaussian characteristics of sensitivity was done. As a results the influence of sensitivity characteristic of used light detector (wavelength of maximum and half-width) on dynamic characteristics of fast light shutter with transmissive TN cell is presented.