I think that the "Bad focus" button is not fully appropriate.
In fact, after about 200 movies viewed, I've often seen ones for which I couldn't tell wether or not there is a track, for many reasons :
- bad focus, but also
- 2 films in one (top focus and low focus imags aren't the same)
- movies where the surface is "too low" (the surface is clear about 2 or 3 images from the bottom of the scolling tool, making impossible to see clearly tracks)
- real movies, i.e. when you scroll, the focus don't change, but the images moves
- etc.
Have I been clear ?