Technical specification for images(1)

Images displayed on this site were created by Steven Gough and Susan Pettigrew of the Digital Imaging Unit of Edinburgh University Library, 2001-2004.

Digital camera back: Phase One PowerPhase™

Resolution: 7072 x 7072 pixels

Uninterpolated files (max 143.3 Mb; min 300ppi)

56mm x 56mm frame capture area

42bit internal colour depth, 14 bit per colour precision

Native File format: Uncompressed TIFF files with Motorola (Mac) or Intel (PC) byte order and header version 6

Capture software: Phase One version 3.1.1 for Power Macintosh

Camera body: Hasselblad 501CM

Lens: Zeiss 80mm (plus 8mm and 16mm extension tubes for close-up work)

Capture: Power Mac G4 400Mhz/Apple 21 inch Studio Monitor with ColorSync

Post-capture edits: Adobe Photoshop 5.0 - CS

Test charts: Standard Kodak Q13 colour separation guide (with metric and imperial scales) and grey scale for reflected work

Lighting: 2 Photon Beard 'Highlight' studio lights: these are cool running, flicker free, 5,400k balanced fluorescent lamps, with a variable output of 2 tubes (110W), 4 tubes (220W), or 6 tubes (330W). This high colour rendering index (Ra 98) (2) light source is designed for digital imaging. The lights are fitted with Perspex safety screens.
Light levels: Using just 4 tubes per light, the measure of Lux @ 1m = 10,666 and at 2m = 3,332. Thus at 1m for 15 minutes the item being imaged would be subject to 2,666 lux-hrs. (By comparison, the standard museum light level for sensitive works on paper is 50 lux. For 6 weeks display at this level (6-day week, 12-hour day) the object would be subject to 26,500 lux-hrs per exhibition). Also, the lights are equipped with reflective barn door units. These are employed to screen the object from light outside the actual scanning periods, thus reducing light exposure to an estimated 2,000 lux-hrs.
Heat rise: A preview scan is obtained in circa 15 seconds. The scan time for a full high resolution (143Mb) image file is typically 5-6 minutes using 4 tubes per light. The rise in temperature at the surface of the copy table during a typical 15 minute total scanning period using 4 tubes per light at 1m (i.e. 10,666 Lux) at no time exceeds 1.25 degrees C. Tests on-site show that the temperature at the object point on the copy table is not more than 1.5 degrees C above the ambient temperature of the room at any time.

Archival equipment: Studio copy table with matt black, soft velvet top surface; Clarkson book supports for bound items (large and medium sets), plus snakes; unbleached pure cotton gloves.

(1) These specifications conform to the Code of Practice for the Submission of Digital Imagery as defined by the Digital Imaging Group of the Association of Photographers (November 1999). [Back]

(2) A measure of the colour shift objects undergo when illuminated by a light source as compared with the colour of those same objects when illuminated by a reference source (daylight) at the same colour temperature. The index range is from 0 (max shift) to 100 (no shift). [Back]

© 2004 Edinburgh University Library / Royal College of Physicians of Edinburgh
02 November 2004

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