On a flight from Geneva to Warsaw, Philip Laven (see his excellent Optics of a water drop ) saw the low sun disappear behind clouds. But his camera viewfinder showed a different scene - a purple sunset. Image ©Philip Laven

"The amazing thing was that, with my unaided eyes, the sun was completely invisible.  However, the purple sun remained clearly visible on my camera for about 2 minutes "

Digital cameras are sensitive to near infrared radiation. Here, the water droplets in the cloud bank have scattered and obscured the direct visible light of shorter wavelength but still transmit a small fraction of the sun's infrared.

The solar image is quite flattened because the picture was taken at fairly high altitude and rays from the sun then undergo differential refraction twice - on entering and leaving the dense lower atmosphere.