Phenomenology of mental imagery can reveal the structure of underlying mental representations, yet progress has been limited because of its private nature. Through a phenomenology-recreation task we elucidate the dynamics of mental imagery. Specifically, the temporal grain, speed of object manipulation, smoothness of contents unfolding, and temporal extent of stability of imagined contents. To gauge these properties, we asked a large cohort of participants (N = 827) to recreate these aspects of their imagination in six tasks. Results showed that temporal features of imagination unfold at distinct timescales, though a factor analysis showed that variance in these tasks could be accounted for via two factors; temporal ability and stability of mental imagery. Additionally, we contrast these regularities with those documented for visual perception, showing that imagined contents are sluggish but more stable than perception. However, both imagination and perception share a common constraint; maintaining identically sized temporal windows of conscious experience.