As the range of materials and applications for holographic and diffractive features grows, so manufacturers can provide customers with a host of options and formats. Increasingly customers are specifying what they require in more detail. This includes material specifications, residual chemical levels, release and adhesion properties, as well as the more obvious image details. To date one feature vital to any buyer that is poorly defined is the optical or diffractive properties of their hologram or diffractive element. The problem is confounded by those manufacturers that do measure or assess the diffractive properties of their products, as there is no agreement on what should be measured and how these measurements should be interpreted. This paper presents a technique that will form the basis of an assessment technique that will allow standardisation, should the industry decide it need it.