Born in 1858 in Aberdeen, Scotland, Humphrey migrated as a young boy with his family to Australia, settling in the Melbourne suburb of Richmond.
Together with Frederick McCubbin and John Mather they established the Box Hill artists' camp, devoting themselves to painting the Australian bush en plein air using impressionist techniques.
In 1896, his riverscape Under a Summer Sun, painted the previous year, was acquired by the National Gallery of Victoria at a Victorian Artists' Society show.
According to art critic Alan McLeod McCulloch, Under a Summer Sun was "probably the first Australian Impressionist work" bought by the museum.
In a foreword to the exhibition's catalogue, Roberts wrote that Humphrey expressed in his works "the intimate and tender spirit of the Bush in its quiet moods", and that, despite his health problems, he "looked forward to a time of leisure for uninterrupted converse with nature.