Auto Focus webcam before snapping image with OPENCV

Question

How do I enable the webcam to auto focus before snapping the image?

My code for capturing the image is as shown:

{
    CvCapture* capture = cvCaptureFromCAM(0); // capture from video device #0


    cvSetCaptureProperty(capture ,CV_CAP_PROP_FRAME_WIDTH , 800); 
    cvSetCaptureProperty(capture ,CV_CAP_PROP_FRAME_HEIGHT , 600); 


    if(!cvGrabFrame(capture))  //if no webcam detected or failed to capture anything
    {              
        cout << "Could not grab a frame\n\7";
        exit(0);
    }

    IplImage* img=cvRetrieveFrame(capture);           // retrieve the captured frame
}

I have tried using wait key, etc, tried googling but to no avail. Does anybody have any idea how I can ensure that autofocus is applied already before snapping the image? Cuz the image now is a little more "blurry" than I would like it.

Answer 1

According to this page "Logitech webcam B910, C910 and C920 Auto-focus fix" it seems that the focus on Logitech C920 webcam is factory adjusted for short and medium distances. The same page has some instructions about changing the factory setup.