J. Cosmet. Sci., 63, 409–412 (November/December 2012) 409 Letter to the editor RALF HAGENS, Beiersdorf AG, Bioengineering—Biophysics Hair Care, Unnastraße 48, D-20245 Hamburg, Germany. We published an article in the September/October 2011 issue of the Journal of Cosmetic Science, entitled “Qualifi cation of an automated device to objectively assess the effect of hair care products on hair shine” (1), which attracted some criticism since then. Since the paper is already published and cannot be amended any more, we feel obliged to address some topics of criticism and provide some clarifi cation by means of this letter. The data provided in the above-mentioned report were generated with a recording device called “opsira Shine-Box,” which was developed between 2006 and 2009 by the authors at Beiersdorf AG in cooperation with opsira GmbH, Weingarten, Germany, and Display Metrology & Systems, Karlsruhe, Germany. This device was developed to assess multiple components of hair shine in parallel, encompassing specular and diffuse refl ection, half width of specular refl ection, sparkle, hair color, and parallelism of hair fi bers using the software tool luca’tool developed by opsira GmbH. The publication describes the level of development in 2009. As a matter of course, neither the overall optical geometry nor the arrangement of illumination, camera, or tress holder inside the device, nor the polariza- tion technique, are genuinely new inventions. They are rather mandatory technical pre- requisites, as published by others before (2), and are found in a rather similar way in several other commercially available hair shine measurement systems such as the Samba system developed by Bossa Nova Technologies, Culver City, California., just to mention one alternative measurement system available in the market. The level of novelty relating to the “opsira Shine-Box” is not the optical geometry of the measurement setup but rather the use and development of new image analysis algorithms for the measurement of hair shine, the measurement of hair sparkle with a dynamic illumination setup, and the use of a cooled camera device. We want to point out that the intention of our report was the qualifi cation of the opsira device as an automated screening tool for hair shine, as routinely performed at Beiersdorf AG. Qualifi cation in this case was done using side-by-side comparison of opsira data with panelist assessments as the standard of reference. We decided to compare the opsira sys- tem with shine evaluation by panelists, because panelists are able to discriminate tresses treated with different rinse-off products, and the new opsira system had to meet all re- quirements of a panel and not the requirements of other measurement systems. Another intention of the report was the presentation of our new measurement of hair sparkle. This measurement of sparkle, which always contributes to the panelists’ subjective assessment Address all correspondence to Ralf Hagens at ralf.hagens@beiersdorf.com

JOURNAL OF COSMETIC SCIENCE 410 of hair shine, is a real novelty and was never published before. The paper was never meant as an advertisement of the opsira device, although it may have been read in this way by representatives of competing technologies for hair shine assessment. This was also the reason why we did not provide an in-depth discussion of the opsira device in relation to other competing technologies. We want to ask all competitors’ forgiveness for not fi nding their devices mentioned or discussed in our paper. The side-by-side comparison of different hair care and styling products with regard to hair shine using the opsira device in parallel with standard panel assessment showed that the automated system provides an almost identical ranking and the same statistical sig- nifi cances as the panel assessment. The algorithms to calculate the bidirectional refl ec- tance distribution function from the point spread function (for the generation of angular-dependent refl ection data coming from the illuminated hair tress) are the core elements of our development and based on different publications by Michael E. Becker, one of our coauthors (3–5). These algorithms are responsible for the good correlation between measurements and evaluation by panelists. Overall, the automated tool com- peted favorably with panel assessments of hair shine, providing clear advantages over panelist assessment in terms of repeatability, workload, and time consumption, as well as sensitivity and specifi city to detect differences after shampoo, conditioner, and leave-in treatment. Thus, it qualifi ed as a routine screening tool. This is the major take-home message of our report, not the superiority of the opsira device over other devices, which was never claimed by us. Another topic of criticism relates to the calculation of luster in our study. The objective shine value or luster (L) was calculated by us using the equation standard specular RS×HW = RD×HW L (1) where RS is the integrated intensity of specular refl ection, RD is the integrated intensity of diffuse refl ection, HWstandard is the half width of an optimally refl ecting area (repre- senting the carrier without mounted hair tresses), and HWspecular is the half width of specular refl ection of the mounted hair tress. We erroneously referred to equation (1) as the “equation of Reich/Robbins” (6), which calculates L as (1/2) ×W S L= D (2) where S is the integrated specular refl ectance and is obtained by measuring the area of the specular peak, D is the integrated diffuse refl ectance and is obtained by connecting the scattered light intensities at 0° and 75° and measuring the area under the resulting line, and W(1/2) is the width of the specular peak at half height of the mounted hair tress.