Jan van Eyck - The Arnolfini Portrait
So many questions, was the wife actually dead when the portrait was painted, is the painting a legal document, can all items be read as symbolic? In any case one of the first oil paintings in western art and one of the first realistic depictions of space and light.
David Hockney in his book Secret Knowledge claims that the painting was probably created with the help of a mirror lense, that is a concave mirror which can focus an upside down image onto a panel. The impressive chandelier apparently was painted without any underdrawing, very unusual for such a dramatically foreshortened form. The telling clue of course is the convex mirror on the far wall which is just the right size if reversed to do the job.