How to reduce SSAO pass resolution ?

Even aftter setting the scalability to 1 (medium), the SSAO pass will still render at 1920x1080 (fullscreen) and takes ~2ms on the GPU. How do I reduce the resolution to something like 960x540 ? I would also like to do this for the Screen Space Reflections as well ( I’m assuming this is the ReflectionEnvironmentAndSky pass )