I forgot. Perhaps the major influence on Weston was Henrietta Shore. Her paintings were somewhat like O'Keefe's, though as it turns out she started making them in that style of modernist simpliciation of form earlier than O'Keefe did. In the 20s more than one reviewer compared their work and found Shore's superior. There is a book of her paintings written by the Art Historian, Roger Aikin. Shore's influence on Weston was not only profound, it was decisive. In his Daybooks, Weston wrote about being moved by Shore's paintings.
Alas, Shore did not have a Stieglitz behind her, pushing her work as O'Keefe did, and she soon faded into obscurity.
I learned this from the book on Shore. Back in 1973 Roger Aikin wrote, what is still the best thing ever written about this subject, comparing the work of Brett and Edward Weston. Shortly afterward, someone suggested to Beaumon Newhall that he might write such an article. He replied, disgustedly, " I started one, by then I saw that it had already been written." Aikin's article always stuck in my mind. Brilliant analysis. Best I have ever read to this day.
So when it came time to find a writer for our series of The Portfolios of Brett Weston, I thought Aikin would be the best one and I searched for him, not knowing a thing about him other than his name (good thing it wasn't Smith). Found him and learned from him about his book on Henrietta Shore.