Complex sentence: Bugiardini was well regarded, and in 1503 he joined the Compagnia di San Luca, the painter's guild, where he met Mariotto Albertinelli, an association that continued until 1509, when Albertinelli moved to the studio of Fra Bartolomeo.
Split into simpler sentences: Bugiardini was well regarded, and in 1503 he joined the Compagnia di San Luca, the painter's guild, where he met Albertinelli. He began an association with Mariotto Albertinelli that continued until 1509, when Albertinelli moved to the studio of Fra Bartolomeo.