Face coverings are causing steamed-up glasses and the tiny particles of water are enough to cause diffraction of light. This is causing a diffraction corona around white lights when I look at them. You can tell that it is diffraction because red is outermost and violet on the inside (my photo has only got red and yellow - I couldn't manage to get a photo of exactly what I saw. With a diffraction grating, n.lambda = d.sin(theta) so larger wavelength red light is spread to a bigger angle. The implication is that it happens with tiny droplets but bigger droplets would produce Mie scattering and then give a white image. This article is brilliant http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/corfog.html#c1 but I suspect I will have plenty of time through the Winter to try to recreate the situations it describes.
