Live-action stereoscopic content production requires a stereo rig with two cameras precisely matched and aligned. While most deviations from this perfect setup can be corrected either live or in post-production, a difference in the focus distance or focus range between the two cameras will lead to unrecoverable degradations of the stereoscopic footage. In this paper we detect focus mismatch between views of a stereoscopic pair in four steps. First, we compute a dense disparity map. Then, we use a measure to compare focus in both images. After this, we use robust statistics to find which images zones have a different focus. Finally, to give useful feedback, we show the results on the original images and give hints on how to solve the focus mismatch.