Image Quality Evaluation by Subjective and Objective Criteria of Sharpness and Gradation with B/W Transparencies

Abstract

The influence of sharpness degradation S (caused by diffusion sheets) and gradation G on the quality of 10 x 16 cm B/W transparencies of four different scenes has been studied. Quality, sharpness and gradation have been judged by 50 observers to yield the scale values Ψ_q, Ψ_s and Ψ_g. The main results are: (1) the judgements of quality Ψ_q, sharpness Ψ_s and gradation Ψ_g form a linear combination which depends on the scene: Ψ_q=a₀+a_sΨ_s+a_gΨ_g. Simple relationships exist: (2) between the photographic y value and the gradation judgements Ψ_g: Ψ_g=klog_γ+B (3) between the sharpness degradation factor S and the modulation transfer function MTF = M(v): S = 1_log M(v)/C.v (4) and between the MTF and the sharpness judgements Ψ_s, dependent on scene and gradation, of the form: Ψ_s = k_s·S+B_s

Zusammenfassung

. Der Einfluss von Unschärfe S und Gradation G auf die fotografische Qualität von lOx 16cm SW Diapositiven mit vier verschiedenen Bildmotiven wird beschrieben. Qualität, Schärfe und Gradation wurden von 50 Personen beurteilt, was zu Skalierungswerten H'Q, 4^ und To führte. Die Resultate sind: (1) Die Beurteilungswerte TQ, Tg und To bilden eine Linearkombination, welche motivabhängig ist: