Charting the Nation - Maps of Scotland and associated archives 1550-1740




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Technical Specification (for images created locally by the Charting the Nation project team)(1)

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 optional 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

Test charts: Industry standard Kodak Q13 colour separation guide (with metric and imperial scales) and grey scale for reflected work; Kodak Q60 target for 5x4 transparencies

Archiving and delivery solutions: Sony DAT DDS3 12Gb tapes (stored off-site) and CD-R Kodak Gold Ultima 650Mb (2) (stored on-site). Copies of each CD-R were provided to the contributing institutions. Discs were written to ISO 660/Joliet format. Kodak claims longevity of 100 years

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) (3) 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
When used on-site the lights are suspended from an IFF top rail system with pantographs. Off-site, the lights are mounted on portable Manfrotto Master Stands
For 5 x 4 transparency copying a Larn electronic high-frequency (cool, no-flicker, optimum colour balance, 5300K) lightbox is employed. Transparencies are stored in acid-free envelopes

Archival equipment: 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) Superseded from February 2001 by Kodak CD-R Ultima 80 (silver-gold alloy, 700Mb). Back
(3) 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

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Published by Edinburgh University Library 
Last Updated: 09-09-2014