By Borden D. Mills
FADGI and Metamorfoze are two sets of preservation standards and metrics developed within the last decade to provide comprehensive numerical analysis of accuracy and quality of digitized image output from a wide array of imaging devices. FADGI (Federal Agencies Digitization Initiative) was first developed in the United States in 2007 as a collaboration between federal agencies to ensure best practices and superior quality for the digitization of still images and audio/visual content. Metamorfoze was developed through a partnership with the National Library of the Netherlands and the National Archives as a series of digital preservation guidelines for two dimensional materials and now is used across Europe and elsewhere in the world.
Both FADGI and Metamorfoze use a tiered rating system to evaluate the quality of digitized content. FADGI uses a rating of 1-4 stars, with one star being the lowest quality and 4 representing the highest (preservation level) quality. Metamorfoze uses three separate categories that correspond to FADGI's 4,3 and 2 star ratings, respectively: Metamorfoze (the highest, or preservation quality), Metamorfoze Light, and Metamorfoze Extra-Light.
Using an integrated method of physical imaging targets and an official, computer-based analysis software known as Goldenthread, FADGI captures and analyses a wide array of color, light resolution and detail metrics at the device and/or object level and separates them into several distinct categories. These categories measure lighting and luminance uniformity, RGB color accuracy, white balance, tone response, spatial frequency response, image noise, color registration, and sampling frequency. From images of an industry accepted test target captured from a specific imaging device, Goldenthread plots the data as a series of charts and graphs which then compares the results alongside a baseline set of industry accepted values in order to determine a final rating.
FADGI ratings can be used to determine a specific digitized output's suitability for display and/or preservation. A four star rating signifies stringent, preservation-level content; a superior comparison of color, tone and detail accuracy between the original, still image and its digitized counterpart. A three star rating signifies fairly accurate digitized content that would be suitable for full color re-printing through most commercial printers as well as high-success optical character recognition (OCR) and searchability. A two star rating may indicate an image suitable for average OCR accuracy and as a means of reasonably accessible online access. A one star rating reflects subpar image quality that would be strictly for direct reference to the original, physical item or for limited, textual purposes only.
While primarily as a means of assessing overall performance of both linear and area array imaging technologies as well as quantifying consistent image quality that meets baseline parameters and other technical specifications, FADGI standards can also be used to better configure and adjust variable digital image capture devices to improve overall image quality. Settings in regards to lighting, color space, lens type, focus, shutter speed, exposure time, ISO speed, aperture setting, and white balance of camera sensors and planetary imaging devices can be objectively analyzed and fine-tuned to optimize capture content as well as streamlining the pre- and post-capture processes involved in the digitization workflow.