Very often, mechanical designs for workpieces include specifications for defined parameters such as roughness or ripple. Polytec white-light interferometers acquire entire 3D profiles in just seconds, where tactile methods would require much longer measuring times. Such parameters – take the percentage contact area or frequency distributions, for example – can be determined quickly and easily. Roughness can be optically determined too, but the values can deviate from the results of tactile measurements to which the drawing dimensions and standards often refer. However, new guidelines for calibrating white-light interferometers give the user the assurance that the measured values can be traced back to calibration standards. Optical measurements also make roughness parameters available. Often, for instance, it is sufficient to decide whether the surface of e.g. dynamic sealing surfaces is too rough – which would lead to high friction losses – or too smooth, which could result in excessive adhesion.