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Digital Imaging Process, Phase 2

This page describes some technical aspects of workflow and procedures used in the current phase of the DAC Digital Imaging Initiative. Each object to be imaged is placed on a copy stand equipped with a Cambo 4x5 Repro camera and a 120 or 180 mm. Schneider Macro-Symmar lens. It is illuminated with Kaiser high-frequency fluorescent lights, generally with diffusion and always with ultraviolet-filtering plexiglas to protect objects from UV light.

The images are made with a Better Light 4000 digital scanning back in the Cambo camera. This yields 5000 x 3750 pixel capture files (with the bit-depth setting most often used, these are 53MB files). White balance, aperture, and exposure (line) time are set manually using procedures developed through quantitative measurement and trial-and-error experimentation. Image files are transferred from the camera to a Macintosh G5 for processing. All images (even those of "black and white" works) are captured, processed, and delivered in color in order to convey subtleties of paper and ink tone that communicate a sense of the original work.

Images are processed with Adobe Photoshop and other applications to perform baseline corrections in a consistent way. A few images require rotating to compensate for minor misalignment at time of capture. After each image is cropped to the area most usefully presented, standard corrections (derived by comparing RGB values in a capture session's images of a Macbeth Color Checker to standard values) then use Photoshop levels, curves, and hue/saturation settings.

After processing, each image is archived as an uncompressed master TIFF. Four JPEGs are exported at sizes tailored to DAC database and web projects. Images are enhanced for sharpness at each size before export. The web images' maximum dimension is 560 pixels; this allows them to be viewed in full on monitors set to at least 832 x 624 pixels, provided the viewer's browser window is maximized and has all of its button and location bars hidden. Image production for monitors of this resolution strikes a balance between serving users with large and not-so-large screens.