Traditionally, it is has been believed that extinction effects due to dust within the interstellar medium of external galaxies are rather small and can be largely ignored. Over the last 10 years however, considerable doubt has been cast over the evidence to support this comfortable idea and it became clear that a more detailed analysis was required. Here, a new technique for mapping the extinction in disc galaxies with high resolution is presented, along with the results of applying this technique to the spiral galaxy NGC 6946.