Piri Halasz writes about several current and recent painting exhibitions on view in Manhattan that together provide a sweeping view of abstraction over the last 70 years. The shows include: Conceptual Abstraction at Hunter College's Times Square Gallery, Helen Frankenthaler, Morris Louis, Kenneth Noland and Frank Stella at Mitchell-Innes & Nash (through November 24), Hans Hofmann: Works on Paper from the 1940s at the New York Studio School, curated by Karen Wilkin (through January 5), and Ronnie Landfield: Where It All Began at the Kenny Gallery, High School of Art & Design.