INTRODUCTION TO BASIC TERMINOLOGY OF DIGITALISATION

Autor:

Joel Leis

Year:

Anno 2015

Category:

Digitisation

ill 1

Raster and vector image. The edges of the ring, enlarged 15 times, are jagged, the vector always retains the shape of an ideal ring.

ill 2

Screen shot. Pixels and the text with jagged edges are visible when enlarged.

ill 3

Resolution. High resolution scanning makes small details visible. The size of the original 25 x 31 cm,  scanned 800 dpi (9400 x 7615 px). Gelatin silver glass plate negative. The hall of Kukulinna manor, 1910.

ill 4

Resolution. 72 pixels per inch or the resolution of the image is 72 dpi (dot per inch).

ill 5

Resolution. 36 lines per inch (36 lpi), the corresponding 72 dpi below.

ill 6

Comparison of resolutions. Scanned resolutions of negatives (grey) and photos (white) made in the Kanut.

ill 7

Comparison of resolutions. Details scanned with different resolutions can be seen in the middle; they have been enlarged to equal the size of the biggest fragment (the upper one 1200 dpi). Their real sizes are on the right.  The graph shows how the 16-bit TIFF file data volume increases depending on the resolution. Gelatin silver photo on paper. August Rebane with his wife and mother-in-law (?)  Photographed by August Rebane about 1923, private collection.

ill 8

Colour bit depth. The image on the left in two colours - black and white, the middle image in 8-bit grey scale, the coloured image three 8-bit colour channels or with 24 bit.

ill 9

RGB colour model. Three basic colours - red, green and blue - provide all the other hues, all the colours together give the white.

The article strives for briefly explaining some technical terms connected with digitisation. Key words are raster data structure, pixel, bit depth, RGB colour model, differences between the JPEG and TIFF files including a survey of colour management. The text has been written with these people in mind who are interested in and in some way connected with digitisation of cultural heritage but have not had the possibility to obtain basic knowledge in the field.

REFERENCES: 

1.      Rahvusarhiivi digiteerimise tehnilised põhimõtted. Rahvusarhiiv 2009. http://www.arhiiv.ee/public/Sailitamine/dig_tehn_pohimotted_2012.pdf

2.      Trükiettevalmistus 1. 2. 3. Ettevalmistus. Värvihaldus. Tüpograafia. Riiklik Eksami- ja Kvalifikatsioonikeskus. Tallinn, 2014.

3.      Technical Guidelines for Digitizing Cultural Heritage Materials: Creation of Raster Image Master Files. Federal Agencies Digitization Initiative (FADGI) – Still Image Working Group, 2009.

4.      Warda, Jeffrey (editor). The AIC Guide to Digital Photography and Concervation Documentation. American Institute for Conservation. Washington, 2011.

5.      Ivar Kaselaid, Marko Levin, Külli Tammes. Värviõpetus, värvihaldus ja trükikvaliteedi juhtimine. Riiklik Eksami- ja Kvalifikatsioonikeskus. Tallinn, 2011.