Correlation of Visually Assessed DOI and Instrumentally Measured Equivalence in Two Types of Instruments

In this study the correlation between quantitative visual assessment of distinctness of image and its instrumental equivalents as measured by two types of measuring instruments namely a goniophotometer and a wavescan DOI instrument was sought after. To this end, 4 scales were prepared based on automotive achromatic samples varying in lightness i.e. black, grey, silver and white, having variable DOI values but the other geometric attributes being kept constant as far as possible. The differences in DOI of samples in each scale were visually assessed and quantified in terms of an also prepared lightness scale by a panel of 16 observers. The coefficient of determination was utilized to assess the correlation between such quantified visually assessed data and the equivalent instrument values as measured separately by a goniophotometer and a wavescan DOI instrument. Results show that irrespective of lightness of samples, the correlation of differences in visual and instrumental data was always superior for the goniophotometer than the wavescan DOI instrument. This implies that the measurement of DOI by a goniophotometer has unequivocal advantages.