GEOMETRIC AND RADIOMETRIC EVALUATION OF THE DSW300 ROLL FILM SCANNER

Geometric and radiometric investigations performed with two LH Systems DSW300 scanners are presented. Their performance evaluation was carri ed out using good quality test patterns and accurate processing method s. The geometric tests include global and local geometric errors, misr egistration between colour channels, geometric repeatability and deter mination of the geometric resolution. Efforts were made to separate th e contribution of various error sources (especially mechanical positio ning, vibrations and lens distortion) on the total error. The radiomet ric tests include investigations of noise, linearity, dynamic range, s pectral variation of noise, and artifacts. After a brief description o f the scanner, details on the above investigations, analysis and resul ts are presented. Regarding the geometric accuracy, the RMS was 1.3-1. 9 mu m and the mean maximum absolute error 4.5-8 mu m. The errors are bounded, i.e. on the average the 3 sigma (99.7%) values are 3 RMS, and the maximum absolute error 3.7 RMS. The co-registration accuracy of c olour channels was about 1 mu m The short and medium term repeatabilit y was very high. With a linear Look Up Table (LUT) the radiometric noi se level is 1 and 1-1.5 grey values for 25 and 12.5 mu m scan pixel si ze, respectively. The dynamic range is 2 D (D ... density) with a very good linear response up to this value. One of the major remaining rad iometric problems is dust. In both geometric and radiometric tests, no significant differences between R, G, B and B/W scans has been observ ed. These results show that the geometric and radiometric quality of t he DSW300 has been very much improved as compared to the DSW200 and al so other scanner models. This test was part of a long and fruitful coo peration between the manufacturer, a major user, and an academic insti tution and shows that honest and critical behaviour, as well as thorou gh understanding of the problems and a desire to search for solutions, can lead to significant improvements to the benefit of all. (C) 1998 Elsevier Science B.V. All rights reserved.