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This research project has two goals. One is to understand the third dimension of colour scales describing the extent of chromatic contents such as saturation, vividness, chromaticness and colourfulness, which are less widely used than the other dimensions, e.g. lightness and hue. With that in mind, the first aim of this work is to derive new models that may serve as an alternative to the third-dimension scale of colour appearance on the basis of colorimetric values. The second goal is to develop important scales, blackness and whiteness. They are widely used because of the popularity of the NCS system. To achieve the first goal, a psychophysical experiment for scaling 15 attributes (Korean corresponding words of “bright”, “light-heavy”, “active-passive”, “fresh-stale”, “clean-dirty”, “clear”, “boring”, “natural-not natural”, “warm-cool”, “intense-weak”, “saturated”, “vivid-dull”, “distinct-indistinct”, “full-thin” and “striking”) using the NCS colour samples was carried out with Korean observers. Each sample was presented in a viewing cabinet in a darkened room. Naive observers were asked to scale each sample using a categorical judgement method. From the results, two scales widely used to represent the third dimension were identified: saturation and vividness. The same samples were assessed by British observers using these two scales. There was a great similarity between the results of the British and Korean observers. Subsequently, more samples were included to scale not only the new third dimension scales (saturation and vividness) but also whiteness and blackness scales. In total, 120 samples were scaled for saturation, vividness and whiteness experiments, and 110 samples were scaled for a blackness experiment. Four sets of models were developed for each of the three colour spaces (CIELAB, CIECAM02 and CAM02-UCS). Type one was based on the ellipsoid equation. Type two was based on the hue-dependent model proposed by Adams (called “the hue-based model”). Each of the above two types was used to fit the present experimental (Cho) data and the NCS data, which were measured using a spectrophotometer. In total, 39 models were developed. The newly developed models were tested using the Cho and NCS datasets. The models that were based on the present visual data were tested using the NCS data. Similarly, the models developed from the NCS data were tested using the present visual data. The results showed that both types of models predicted visual data well. This means that the two sets of data showed good agreement. It is also proposed that the four scales (saturation, vividness, blackness and whiteness) based on CIECAM02 developed here are highly reliable.

A large scale experiment was carried out to accumulate colour difference discrimination data for lighting stimuli which were simulated on a display. Twenty six colour centres were selected and twenty one pairs of chromaticity difference were prepared surrounding each colour centre. Each pair was assessed using ratio method against a grey and a black background by a group of 20 normal colour vision observers. Both white and coloured lighting stimuli were used; corresponding to specifications for the solid state white lighting products and part of the MacAdam colour centres respectively. The latter defined the fundamental research for visual sensitivities known as just noticeable difference (JND). The results were used to test colour spaces and chromaticity diagrams as well as to evaluate colour difference predictions of various colour difference formulae and colour appearance models. It was found that u'v' chromaticity diagram can represent colour discrimination data for lighting colour stimuli more uniformly. Moreover, CIELUV colour difference formula performed better in predicting colour differences for lighting stimuli; especially when using black background. It performed better than CIEDE2000 and CAM02-UCS formulae, which were derived based on surface colours, even though it has been shown in the previous studies that these perform well when simulating surface colours on display. These points also support that the experimental arrangement could potentially be used to simulate light sources (luminaires) in order to evaluate them as lighting stimuli. Furthermore, the visual results obtained against the black background can mostly be predicted better by the models than those against the grey background for lightning stimuli.

Quantifying the appearance of coating products is essential in the automobile and automobile finishing industries for efficient product development and product/quality control. There is a specific need to develop techniques to measure the total appearance of metallic coatings. The present study focuses on two key attributes of visual texture: coarseness and glint. In order to develop models to capable of measuring these attributes, it was first necessary to design psychophysical experiments for assessing coarseness and glint as perceived on metallic-coating panels. The change in the appearance of the metallic coatings is known as a gonioapparent effect, and is greatly dependant on the illumination and viewing conditions. Therefore, appropriate conditions were carefully examined for the independent observation of coarseness and glint in order to discern those attributes. It was found that diffuse illumination was appropriate for viewing coarseness and directional illumination was appropriate for observing glint. Under these appropriately-controlled conditions, the perceptual coarseness and glint of sets of metallic-coating panels were assessed by human observers. A digital camera was used to capture information on the spatial detail of the metallic-coating panels. An image of each panel was captured under the same viewing conditions as used for the visual assessments. The information in a single image was sufficient to represent a metallic-coating panel under identical diffuse illumination conditions for which observers assessed coarseness. For capturing information on glint, however, a high dynamic-range (HDR) image was necessary because the dynamic range of the scene in which the glint was observed exceeded that of the camera used in this study. Two computational models were developed to predict perceptual coarseness and perceptual glint by extracting associated features from the captured images. The performance of these models was verified by comparing predictions made using them with the perceptual coarseness and glint scaled by observers. For industrial use, the visualisation of products on computer displays would give various opportunities, for example, to develop and design products or coatings and also to communicate appearance information. A digital camera and a suitable display would enable this to be achieved, but the ability to reproduce the appearance of metallic-coating products on displays in a satisfactory manner was found to have significant ~ challenges. The coarseness model developed in the present study was able to represent perceptual coarseness based on the images captured by the digital camera. However, the resolution of the images was not high enough to resolve the individual aluminium flakes contained in the coatings, which contribute to the visual texture. Therefore, verification of the images was carried out for the coarseness attribute by comparing the coarseness perceived in the images displayed on a liquid-crystal display (LCD) with the metallic-coating panels themselves. In addition to camera limitations, LCD resolution also prevented the same conditions used for physical panel assessment from being replicated. Therefore, two optimal conditions were selected and perceptual coarseness was scaled using images. Besides the difference in experimental conditions, there was also a difference in the "absolute" texture appearance between the two media because of errors in image reproduction of the images. In spite of this, the relatively-scaled perceptual coarseness for the image samples agreed well with that for the original physical samples. This implies that it is practicable to assess perceptual coarseness from an image on a display that simulates a metallic-coating panel.