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