November 3, 2004 � Two weeks ago, a professor at Cornell University made digital imaging headlines by creating his own resolution test chart. He made his chart available for free download on his school web site. Stephen H. Westin, a computer graphics professor, semi-manually made the ISO 12233 resolution chart to aid in research at Cornell.
�I have been using digital cameras for measurement purposes in my research for some time, and one of our students was trying to characterize a particular camera and it seemed useful to have the ISO 12233 chart,� Westin said. �A fair amount of work, actually, as I was working from an Excel spreadsheet with the coordinates of the outlines of the various elements of the chart.�
Magazines, review sites and manufacturers use the ISO 12233 chart to test the true resolution of digital cameras. Professionals pay anywhere from $150 to $900 for the industry standard chart. Westin�s version is not meant to compete with the original chart, but to inform the general public and encourage home experimentation.
�I�m not competing with the commercial sources,� Westin said. �If you really want to conduct a test that meets ISO 12233, you need to know what you are doing; get a copy of the ISO standard and get a print of the chart that you know is good, rather than something you happened to run off on your home printer.�
Downloading the chart is easy. However, printing can be more difficult. The chart must be printed at the highest resolution possible. Once printed, users can compare digital cameras by taking pictures of the chart and evaluating the blurriness of the lines and the smooth or pixellated edges of shapes. Consumers can check out Westin�s chart at http://www.graphics.cornell.edu/~westin.