Narrowband tunable filters play a key role in advancing the capabilities of multispectral and hyperspectral imaging (HSI and MSI) systems. Yet, some challenges limit their effectiveness including low optical throughput, slow response time, and limited tunability range. In this Letter, the common path Sagnac setup was employed to obtain a fast and polarization-independent narrowband tunable filter using liquid crystal (LC) wave plates at both the folded and fan Solc configurations. The filter provides full tunability over the visible range for multiple orders of transmission peaks. The setup allows the collection of both the S- and the P-polarization components with a total throughput twice that of the polarization-dependent Solc filter. The enhanced throughput enables using a larger number of LC retarders at relatively thin thicknesses, thus obtaining a shorter response time. The Sagnac common path configuration helps in miniaturization and minimizes the effects of LC thickness variations.