Range for camera exposure time

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Hi, I want to get and set exposure time with function get(CV_CAP_PROP_EXPOSURE) (page 352-353 in opencv reference manual). value return for my camera (logitech webcam) is -5. When I use debugger in file cap_dshow.cpp min and max value for exposure time are -12 and -1 with a step of 1. Is it possible to retrieve those values with opencv ? thanks for yours answers