Hybrid perovskite photovoltaics could play a vital role in future's renewable energy production. However, there are still severe challenges when scaling the technology. In this work, perovskite solution films drying in laminar and slot-jet air flows are investigated extensively by optical in situ characterization. The main results are a quantitative model of perovskite drying dynamics and a novel in situ imaging technique - yielding valuable predictions for large-scale perovskite fabrication.