I met a strange phenomenon when I processing the cryo-EM with a smaller number of movie frames.
Usually, the mask shows a similar shape as the map as Fig. 1 (using full-frame).
But a hat-shaped density appeared in my mask as Fig. 2 (using patch-frame).
I want to know how to overcome this strange-shaped mask (adjust some parameters of dynamic mask? I tried several, but did not work), even though it may not influence the map refinement result.