unfortunately, y the time and image becomes a jpeg, it's almost impossible to determine if it was originally shot in HDR mode unless you compare it to an image that was not. In HDR mode, the D600 is working in 14-bit color which means the range of colors for red, green and blue is 16,384 shades. When the camera converts that to jpeg internally, it drops the number of shades down to 256. So the range of colors from 0-255 will be greater in your image but they will also be truncated into the limited 8-bit 256 range.