This code in Python used to bring up the DirectShow properties dialog for setting the exposure, brightness, etc. for a camera but at some point (not sure how long ago), it must have stopped working as it doesn't work for me anymore, even trying across different computers and different cameras:
cap = cv2.VideoCapture(0)
cap.set(cv2.CAP_PROP_SETTINGS, 1)
Here's the window I'm referencing https://cdn4.xsplit.com/cms/broadcaster/getting-started/Adding-a-Webcam-4.png
Python 3.6, OpenCV 3.4