MOOCs promised to herald a new age of open education. However, efficient access to MOOC content is still hard, thus unnecessarily complicating many use cases like efficient re-use of material, or tailored access for lifelong learning scenarios. One of the reasons for this lack of accessibility is the shortage of meaningful semantic metadata describing MOOC content and the resulting learning experience. In this paper, we explore Concept Focus, a new type of meta-data for describing a perceptual facet of modern video-based MOOCs, capturing how focused a learning resource is topic-wise, which is often an indicator of clarity and understandability. We provide the theoretical foundations of Concept Focus and outline a methodical workflow of how to automatically compute it for MOOC lectures. Furthermore, we show that the learners' consumption behavior is correlated with a MOOC lecture's Concept Focus, thus underlining that this type of meta-data is indeed relevant for user-centric querying, personalizing or even designing the MOOC experience. For showing this, we performed an extensive study with real-life MOOCs and 12,849 learners over the duration of three months.