title: Is there a criteria for the size and position of bounding box of detected face
body: <p>I'm trying to assess the accuracy of my face detection code. But the data set is a video clip where the person in the image turns his head from side to side, so this clip contains both frontal and profile faces.</p>
  
  <p>I'm using Viola-Jones face detector in OpenCV and it would fail on some profile faces and the bounding box might become very small or large sometimes even on some frontal faces.</p>
  
  <p>My question is that is there a criteria for the size and position of bounding box of face?</p>
  
  <p>When trying to annotate ground truth of faces manually， I'm not sure whether the bounding box should be a little larger than the face or it should be just as large as the face. Besides, when comparing the detection result with the ground truth, even the result position coincides with the ground truth, the result size could be too small or too large. So I want to see if there is any criteria for the size of detected faces.</p>
  
  <p>Many thanks!</p>