Some web cameras have a special button to capture frames than button pressed. This function is called still frame capture.
In Video Capture SDK .Net, you can use the following code to catch still frames.
Set Video_Still_Frames_Grabber_Enabled to true before you call Start in your code.
Use OnStillVideoFrameBitmap / OnStillVideoFrameBuffer events to get all frames.
Use the Frame_Save method to save the frame to file.
Use the Frame_GetCurrent method to get the frame as Bitmap.