The gamma control is not available for the selected camera
This VB example uses the minimum and maximum gamma values to initialize the slider control:
Private SubForm_Load() Slider1.Min = ActiveDcam1.GetGammaMin
Slider1.Max = ActiveDcam1.GetGammaMax
Slider1.Value = ActiveDcam1.Gamma
If the currently selected camera doesn't support software gamma control, the method will generate an error.