C) Florentine Influences on Piero della Francesca's work
Brunelleschi's Hospital of the Innocents (Ospedale degli Innocenti) is begun in 1419; by the time Piero della Francesca comes to Florence in 1439, the building is complete except for the bas-reliefs meant for the roundels on the facade.
Certainly Piero is favorably impressed by Brunelleschi's ideas of one-point perspective and classical proportions for architecture, because when he comes to paint an Annunciation in the gable of an altarpiece for nuns in Perugia, at the convent of Sant'Antonio da Padova in 1462, he uses one-point perspective in a dramatic way, and he imitates the columns, Corinthian capitals, and rounded arches he would have seen on the portico of Brunelleschi's Ospedale. (The altarpiece is now in the Pinacoteca Nazionale dell'Umbria in Perugia.)While he could have looked at similar columnar progressions in San Lorenzo and for Santo Spirito, the columns in this Annunciation resemble most closely those of the Hospital.
For a considerably larger
The column set between angel and Virgin in Lippi and Fra Angelico's versions of the Annunciation seems to have carried over into Piero's image.
The position of the dove above Christ is very much like the foreshortened dove hovering over Christ in Ghiberti's Florentine Baptistery panel from the North door of 1403-25:
Piero's bird is viewed slightly more head on, but the colors of stark white against deep blue pay homage to the colors of tin-glazed terracotta he would have seen in Florence. The spirit hovering over Christ reflects the spirit hovering over Piero's creative process. The beauty of the white flight in air holds captive the viewer of both scenes. As we watch, both birds suspend belief.