Monet and Renoir, friends collaborating in open air about 1865, discovered that sunlight filtering through a canopy of tree leaves does not produce the splotches and dapples that studio artists conventionally represented at the time but circles of light. Sometimes the circles of light punctuating the shade are clear, separate and crisp, as though light is being propagated as particles, but if the pin-hole gaps between leaves are very close together, they will project compound or superimposed circles that look like the waves that Thomas Young saw in his double slit experiment in 1803-4. Newton’s Opticks published in 1704 had convinced most scientists during the eighteenth century that light traveled as corpuscles. Shortly after Young showed that light behaved as waves, most scientists for the rest of the nineteenth century were convinced that light behaved as waves. Not until the twentieth century did scientists realize that light behaved like both waves and particles. Because Renoir and Monet were not burdened with optical theories but closely observed the nature of light with acute eyes, they began in 1866 to represented light under trees as both single particle-like and compound wave-like circles. The circles were images of the sun being projected through pin-holes between leaves from the tree canopy overhead. Leafy branches with pin-hole lenses were nature’s cameras reversing circular images of the sun onto the ground. The discovery of sun-circles represented in the paintings of Monet and Renoir has until now been ignored. It is time we recognized their achievement.