Not since Mr. Reese introduced peanut butter to chocolate has there been such an inspired pairing as this show of more than 40 O'Keeffe paintings and more than 50 Adams photographs. The two met during their first extended stay in New Mexico in 1929, when she was 42 and he was 27. She eventually settled there, while he continued to visit. "Natural Affinities" refers not just to the friendship they maintained for the rest of their lives but also to their connection with the distinctive landscapes of the desert Southwest. The results were documented in the often-wonderful juxtapositions of this exhibition, which enhanced our appreciation of both artists in equal measure.