The black cloud is probably colored or transparent stroked paths. All stroked paths become 100% opaque and black during a morph.
You should remove the unwanted paths or use SVG images that only contain black stroked paths of 100% opacity .
-Mike (videoscribe user)
I'm not using SVG images (just JPEG and PNG). How are SVG created?
I am trying to have an image morph into the screen as shown in the tutorial.
The problem is that as it's morphing I see a black cloud growing, then the image appears at the end. What is the black cloud? I don't think I did anything differently from the instructions given in the tutorial.