Are you suggesting you have a specific range that the reading ends at? If so what's the range? BTW, What controller are you using?
My Lib read approximately (fast, not accurate), the light intensity. This select the area (dark, normal, bright) and than retrieve brightness accurate. The range is 0.11 lux to about 190,000 lux (not very precise at end of range).
My controller software ist FHEM on a Cubietruck.