A new extended color space camera, "XTF (eXtended Tri-angular Format) ", is proposed, where, through the use of YRGB color separation, RGB color signals are modified to obtain negative primary colors (those outside the RGB triangle) : the difference between Y (a taken luminance signal) and Y' (the calculated luminance signal, i.e., the weighted sum of taken R, G and B colors) is allotted to the taken R, G, B colors. The ratios of allotting it to these colors are decided, e.g., inversely-proportional to these taken color signals, respectively. Computer simulation confirmed that the "XTF" camera performs well.