| Accurate colour measurement is a very important factor to determine the quality of finished products in the colour-related industries, such as paint, printing or textiles. The objective colour communication method is an method to enhance both colour matching and colour assessment. Because of advances in spectrophotometry and information technology, colour quality may be expressed in a digital format and communicated to other parties by electronic means.; The spectrophotometer is one of the important instruments for colour matching and colour measurement. Most of the modern spectrophotometers have satisfactory repeatability and the suppliers of these instruments claim that the repeatability of the measurement on the same instrument is lower than 0.01 CIELAB ΔE units. In this research project, it was found that the repeatability of the advanced spectrophotometers ranged from 0.044 to 0.112 CIELAB ΔE units for the dual beam spectrophotometers while, for the single beam spectrophotometer, the repeatability ranged from 0.115 to 0.377 CIELAB ΔE units.; When considering the inter-instrumental agreement of different makes of spectrophotometers, the manufacturers also claim that the inter-instrumental agreement of those of similar design is lower than 0.15 CIELAB ΔE units. However, in this research, it was found that the inter-instrumental agreement between the spectrophotometers manufactured by the same manufacturer ranged from 0.526 to 0.611 CIELAB ΔE units. The inter-instrumental agreement between the spectrophotometers manufactured by different manufacturers ranged from 0.575 to 0.854 CIELAB ΔE units.; Since the inter-instrumental agreement of the spectrophotometers is very low, various mathematical models have been developed in order to improve the inter-instrumental agreement between spectrophotometers. In this project a new mathematical model, named the R-Model, was developed using both GLOSSY and MATT Ceramic Tiles. Spectral data from 400–700 nm was analysed using the concept of bandpass correction as well as the multilinear regression method. The performance of R-Model was found to be better than that of the previous models. The improvement of the inter-instrumental agreement was up to 90% for the ceramic tiles. Moreover, the inter-instrumental agreement for the other coloured samples such as textile and paper samples also improved accordingly, from 26.1% to 57.6% and 13.7% to 61.1% respectively. |
