title: OpenCV connection between keypoint size and octave
body: <p>I am working with <strong>OpenCV</strong> <strong>keypoints</strong> and I got a questions about keyPoint size and octave.</p>
  
  <p>I know that a keyPoint have a coordinate (x,y) and size which simply can be described as a circle with (x,y) center and radius of size.</p>
  
  <p>And I know that there are some octave levels (during which the image is being downsampled by 2) that the keyPoints are being detected. </p>
  
  <p>I have 2 questions about this.</p>
  
  <ol>
  <li>Is there a some relationship between the <strong>keypoint size</strong> and the <strong>octave or sublevel</strong> when it is detected?</li>
  <li>What is the maximum number of <strong>octave levels</strong> that image can have? As at every octave level the image is being downsampled by 2 does that mean that the answer is Log(2,image_size)? And what about <strong>sublevel</strong> ?</li>
  </ol>