how to change usb_cam parameters?

edit

Hello. I have installed usb_cam package. And making use of it with visp_auto_tracker:

roslaunch visp_auto_tracker tracklive_usb.launch

But the camera looks quite bright, i would like to edit those parameters (brightness, contrast, etc.) as easily as with dynamic_reconfigure and uvc (which i used for a totally different project):

rosrun dynamic_reconfigure dynparam set /uvc_cam_node contrast 90

Please help.

Greetings ROS community.