1. An automatic light-responsive light shutter comprising: light shutter means responsive to application of a control signal at a first level for passing light therethrough along a first path and responsive to application of said control signal at a second level for highly attenuating light passing therethrough along said first path; first light responsive means for sensing intensity of direct light which strikes said light shutter means generally along said first path; second light responsive means for sensing intensity of side light which strikes said light shutter means generally perpendicular to said first path; circuit means for providing a comparison signal at a level which is a function of the relative intensities of direct and side light sensed at said first and second light responsive means, respectively; and control means responsive to said comparison signal for applying said control signal to said light shutter means at said first level when said comparison signal level is within a first predetermined range of levels, and for applying said control signal to said light shutter means at said second level when the comparison signal level is within a second predetermined range of levels, said first and second predetermined ranges of levels being substantially adjacent one another.