In another series of works, Greenfield takes photos of turn-of-the-century blackface performers and superimposes a subversive message that looks like an eyechart.
Some eye-care offices have a device called an accommodation rule that allows a technician to slide an eyechart back and forth to simulate different distances.
But really, there's more to this than meets the eye: according to a chart compiled by the Korea Trade-Investment Promotion Agency, the total number of mobile phones sold domestically between 2002 and 2004 declined steadily.