• Use a greyscale stepwedge alongside the image to calibrate your tones. Photograph this with the image as a known tonal reference point. A step wedge is a tonal scale from white though grey to white, manufactured by companies like Agfa and Kodak. The wedge or tonal scale is photographed along side the work as an accurate reference as to the tones of an image. Say the image was a black and white painting but it was predominately black with little white. In the reproduction of the work, it becomes difficult to work out exactly where true black is and where the intermediate grey tones fall. The set wedge acts a known reference point.