Michelangelo said those doors were beautiful enough to be the Gates of Paradise. He may have thought that or he may have said so just to be nice. It is hard to believe that he would have made the same mistakes Ghiberti made.
What doors? Lorenzo Ghiberti’s bronze doors of the Baptistry of St. John’s in Florence. They are covered with gilded bronze reliefs showing scenes from the Old and New Testaments and they are some of the most famous sculpture ever made.
Painters weren’t the only ones to go crazy over the newly discovered laws of perspective: sculptors tried to use them too. Ghiberti had an infallible eye and probably no one could make relief pictures that followed those laws better than his bronze plaques. But rather than prove that using those laws you can have depth in a relief, including landscape in the background, Ghiberti’s doors show that you can’t—at least that you probably shouldn’t. Good as the doors are, they seem to be simply in the wrong medium. They should have been paintings.
Those laws of linear perspective were not made for sculptural relief. There is too much plain drawing on Ghiberti’s bronze; and the trick of lower and lower reliefing as the figures and buildings recede into the background doesn’t really work unless one’s eye has already been educated by looking at a lot of paintings and is willing to play along. When the sun shines on the flat bronze slabs and casts its inevitable shadows, the whole trompe l’oeil is exposed: the half-modelled figures in the distance cast their shadows the same as the fully-modelled figures in the foreground and pop right out of the plaque. And their shadows don’t give a hoot for the careful perspective lines that were laid down to guide the eye. Those shadows obey the sun. You might be reminded of the problem desert soldiers had to camouflage their trucks and artillery so that enemy airplanes wouldn’t see them. They painted them the same color as the sand but still the planes had no trouble spotting them because of their stubborn shadows.