Abstract: This paper presents a fast color-to-gray conversion algorithm which robustly reproduces the visual appearance of a color image in grayscale. The conversion preserves feature discriminability and reasonable color ordering, while respecting the original lightness of colors, by simple optimization of a nonlinear global mapping. Experimental results show that our method produces convincing results for a variety of color images. We further extend the method to temporally coherent color-to-gray video conversion.