A million years ago, when I was in the Whitney Museum Independent Study Program, the program left New York City for what I believe was the only time and spent the summer in New Mexico. David Diao, Ron Clark, and a few others visited Agnes Martin.

What they may have thought would be a studio visit became something else.

Instead of taking them into the studio and showing them paintings, Martin took them on a long hike on a very hot day to see a remote tree she insisted they had to see.

When people first encounter Bridget Riley's stripe paintings, they often assume the work is highly calculated. The stripes appear so precise, so controlled, that it is easy to imagine a system determining the outcome.

The reality is more interesting.

Riley was not trying to make a system. She was trying to understand color.