Psychophysical evaluation of large sample sets was studied with reference to the International Newspaper Colour Quality Club Jury Evaluation, in which 150 prints of the same image are assessed by category judgement under 10 different quality attributes. In a series of experiments using sub-sets of the CQC prints, some psychophysical techniques which could affect the reliability and precision of the results were evaluated. It was also possible to gain insights into the relationship between the different psychophysical methods. On the basis of these results a number of modifications to the category judgement task used in the Jury Evaluation are proposed. These include the adoption of an anchor image whose scores on the quality attributes are defined in a preliminary observer task; and a reduction in the number of attributes and judgement categories.