Softcopy quality ruler method: implementation and validation

Elaine W Jin; Brian W. Keelan; Junqing Chen; Jonathan B. Phillips; Ying Chen

doi:10.1117/12.805922

19 January 2009 Softcopy quality ruler method: implementation and validation

Elaine W Jin, Brian W. Keelan, Junqing Chen, Jonathan B. Phillips, Ying Chen

Proceedings Volume 7242, Image Quality and System Performance VI; 724206 (2009) https://doi.org/10.1117/12.805922
Event: IS&T/SPIE Electronic Imaging, 2009, San Jose, California, United States

Abstract

A softcopy quality ruler method was implemented for the International Imaging Industry Association (I3A) Camera Phone Image Quality (CPIQ) Initiative. This work extends ISO 20462 Part 3 by virtue of creating reference digital images of known subjective image quality, complimenting the hardcopy Standard Reference Stimuli (SRS). The softcopy ruler method was developed using images from a Canon EOS 1Ds Mark II D-SLR digital still camera (DSC) and a Kodak P880 point-and-shoot DSC. Images were viewed on an Apple 30in Cinema Display at a viewing distance of 34 inches. Ruler images were made for 16 scenes. Thirty ruler images were generated for each scene, representing ISO 20462 Standard Quality Scale (SQS) values of approximately 2 to 31 at an increment of one just noticeable difference (JND) by adjusting the system modulation transfer function (MTF). A Matlab GUI was developed to display the ruler and test images side-by-side with a user-adjustable ruler level controlled by a slider. A validation study was performed at Kodak, Vista Point Technology, and Aptina Imaging in which all three companies set up a similar viewing lab to run the softcopy ruler method. The results show that the three sets of data are in reasonable agreement with each other, with the differences within the range expected from observer variability. Compared to previous implementations of the quality ruler, the slider-based user interface allows approximately 2x faster assessments with 21.6% better precision.

Citation Download Citation

Elaine W Jin, Brian W. Keelan, Junqing Chen, Jonathan B. Phillips, and Ying Chen "Softcopy quality ruler method: implementation and validation", Proc. SPIE 7242, Image Quality and System Performance VI, 724206 (19 January 2009); https://doi.org/10.1117/12.805922

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