We pose the image reconstruction problem for pictures distorted by rolling shutter as an observability problem. In particular, we study the observability properties of linear systems of whom measurements are taken with a pixel-by-pixel evaluation. We do not concentrate on the technical process behind rolling shutter, but introduce and study it as a systems theoretic property. Assuming recurrences in the time series of pictures which we aim to reconstruct, we derive resonance-like conditions for observability.