Ronian's latest paper has been published in the European Journal of Physics! In this new work, Ronian extends conventional optical radiometry to the case of non-stigmatic, non-aplanatic, and non-isoplanatic lenses. In other words, you can now apply the image "brightness" calculations from radiometry to any lens, such as commercial off-the-shelf lenses forming the image of any source onto a sensor. Click HERE to read the open-access author-accepted preprint!