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topography and optical properties. The phrase ���surface roughness��� now embodies a family of sub-definitions, Rx, where different definitions represent peak-to-trough, root mean square or other definitions. Other, more mathematical concepts for surface characterization include texture and curvature; and optical properties have long been characterized in terms of specular reflectance (also known as gloss). More recently, parameters such as Distinctness of Image (DoI) have also been introduced. Still widely used today, one of the oldest methods for surface roughness measurement is profilometry, where a micron-sized stylus records surface topography as an electrical signal that can then be processed. In the last 10 years or so, a range of optical, non-contact methods have been developed, the oldest being interferometry. More recently, a technique known as phase stepped deflectometry has been developed 24 JANUARY 2013 in France, offering many advantages over older optical and other techniques. ExpErimEntal rEsults A highly reflective surface may have random defects such as scratches or pits that can be too small to be observed by the naked eye. More important, however, is the question of isotropy (uniformity). As a result of mechanics of the polishing process, there are often systematic variations of property along the X and Y axes, and some such effects are revealed in the data reported below. Using an Elcometer 7061 MarSurf PS1 profilometer, roughness data was obtained as shown in Table 1. These measurements already reveal significant differences between the products of the three manufacturers, with manufacturer R scoring best. A number of other authors have studied the relationship between surface roughness and reflectance or gloss, but there���s no discernible trend. Electrodeposited chromium with an air-formed oxide film is chemically very similar to stainless steel. The sample here is described as ���mirror-polished stainless steel,��� with a roughness, RZ, of less than 1��m, probably less than 0.5��m. Table 2 shows data for the three samples, obtained using an Elcometer 6015 goniophotometer. The gloss measurement is taken at a 20-degree angle with the unit calibrated using a mirror tile. The parameters in the table all are referenced to standards. Broadly speaking, DoI is a characteristic of the surface at the 0.1 mm wavelength, haze at 0.01 mm wavelength and gloss at 0.001 mm wavelength. Gloss is defined in ISO 2813/ASTM D523, measured at 20 and 60 degrees. R(spec) is a measurement of peak reflectance defined in ASTM D430, haze is specified in ASTM D430, and