Abstract: We present symTone, a dual-mouse, symmetric image manipulation application. symTone includes a symmetric method for manipulating a tone reproduction curve using two standard USB mice. The symTone technique is an important contribution because the two mice are manipulating a geometric object as a tool to improve the underlying digital image, thus a spatial object (the curve) is being used to manipulate non-spatial data (the image tones). Our empirical evaluation of the technique shows that symmetric interaction can be effective for manipulating non-spatial data. This novel technique offers a significant improvement in ease of use and is a precursor to more advanced symmetric tone-mapping applications.