Webcam frame from Aforge always gray image

I am using Aforge .NET framework to get a webcam in my app but I always get an all gray image frame.

            this.videoSource = new VideoCaptureDevice(this.Moniker);
             this.videoSource.DesiredFrameSize = GetHighestResolution(this.videoSource.VideoCapabilities);
             this.videoSource.NewFrame += new NewFrameEventHandler(videoSource_NewFrame);
             this.videoSource.Start();
 

The vent handler:

    private void videoSource_NewFrame(object sender, NewFrameEventArgs eventArgs)
     {
         this.outputBox.Image = (Bitmap)eventArgs.Frame.Clone();
     }
 

This should do the trick. DesiredFrameSize is set to the highest value the cam can support.

Any hints why the image is always gray? Even when writing it do disk...

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