During one scene, I was able to count four rows of contrasting color and eight rows of the main color in between the two contrasting color bars. (No wonder those scarves are so freaking long!) Right now I'm guessing there is at least forty rows between the trapped sets, but I'll have to try and get a better look tomorrow when Scott and I go to see it again.
At the second task, Neville is wearing a scarf of all four house colors in the trapped bar design with black as the main color.
Why do I have the feeling I'll be knitting more HP scarves this winter?