why is the camera auto-focusing inspite of being in manual mode? I am trying to take video for a time lapse of stuff I write on white paper. Issue is that when the paper is blank, it looses its focus automatically. Unitl something or some writing/drawing/object is put on the paper the focus will wander off. 

All this happens even when my camera is in manual mode.

Here is a sample:


                
            

First I want to understand why it happens, and, how to avoid it. I own a canon powershot sx 520 hs
It looks like by default, that camera fine-tunes the focus (even in manual focus).

From the Canon support page: To deactivate automatic focus fine-tuning when the shutter button is pressed halfway, choose  -> [  ] tab -> [Safety MF] ->[Off].