ISO 12233 defines the slanted-edge technique for estimating the spatial frequency response (SFR) of imaging systems. SFRMAT, originally developed by Burns, has served for over two decades as the de facto MATLAB implementation of this standard. This paper presents a fully open-source Python implementation of SFRMAT5 with equivalent functionality and numerical fidelity. The software mirrors the original MATLAB structure to simplify maintenance and coexistence, while supporting CLI, GUI, and headless operation. Validation against the MATLAB version demonstrates practical numerical equivalence (< 10−10) on real captures where valid outputs are available. The implementation enables broader adoption in research, education, and production imaging pipelines and is available at burnsdigitalimaging. com/ software/ sfrmat .