C++ access to Auto/Manual Gain

Archived from groups: alt.comp.periphs.webcam (More info?)

Is there a webcam out there that will give me some type of SDK or
DirectShow access to the Auto Gain functionality of the webcam itself?
I have a Logitech 4000 Pro that DOES Auto and manual gain but the only
way to turn it on and off is through their User interface. Logitech,
for some unknown reason, does not make this accessible either through
an SDK or the DirectShow's VideoProcAmp and CameraControl COM
interfaces. Even if I hack through their UI and simulate button clicks
and whatnot, the UI disables certain sliders and, worse yet, when in
Auto mode, CENTERS them so I cannot read the current gain and exposure
values while in Auto mode. (sigh!)

I am working on a security application and need access to the gain and
exposure to handle all different types of lighting conditions.

Apparently Logitech will not reply to any emails regarding this issue.