Wine Glass Caustics
The optical phenomenon called caustics is observed in this image under room light illumination, which results in the light interacting with the curved surface of the wine glass to form a colored ring in the center of the glass containing Finnish Glögi. The image was captured in Joensuu, Finland with a smartphone camera with EXIF data and post-processed with a camera filter. EXIF data: ISO:500, S:1/33 s, EV:0, F: 1.8, focal length: 140 mm (equivalent to 35mm focal length film).
—Dipanjan Das, Early Stage Researcher, Finland