A New Direct Tonal Evaluation Method for the Digital Photography System (2)

• Published in: Journal of The Society of Photographic Science and Technology of Japan Vol. 68; no. 2; pp. 152 - 159
• Main Authors: FUNYU, Nozomu, OGAWA, Makoto, NAITO, Akira, TANAKA, Masuo, OHNO, Shin
• Format: Journal Article
• Language: Japanese
• Published: THE SOCIETY OF PHOTOGRAPHY AND IMAGING OF JAPAN 2005
• Subjects: camera-through sensitometry; hardcopy evaluation; softcopy evaluation
• ISSN: 0369-5662; 1884-5932
• DOI: 10.11454/photogrst1964.68.152

This paper discusses the new methodology for the direct evaluation of the tonal characteristics of digital photography system. The new evaluation method is based on the lightness measurement of the displayed reproduction linear lightness step chart image on the PC monitor operated by graphic software. It was named thesoftcopy-evaluation. On the digital photography images shot by digital still camera, DSC, the dark low-key images tended to be disturbed by random noise generated by sensor itself and thus the light high-key images are preferable for the high definition digital photography pictures. The effects of DSC for the tone reproduction were distinctively appeared on the high density region of the current densitometric curves using the linear density step chart. It was not clear in the low density part so called highlight region. The authors proposed the new divided linear lightness step charts of the highlight, mid-range and the dark shadow regions. These were modified the original full range lightness linear step chart to compress and expand the input the data level coordinates. The results of the softcopy-evaluation to measure the lightness of reproduction step chart images on the PC monitor, the slopes of lightness characteristic curves were apparently affected by DSC using the chart shooting. Even in the result of blight highlight chart, the slope of lightness characteristic curves of the DSCs were apparently dispersed. As the results the effect of DSC on the tonal characteristics of the reproduction images were distingished in the every tonal regions of the photographic reproduction. These results were also suggested that the selection ofDSC models tended to be the same effect as the selection of film on the current silver halide photography.