THE DIGITALISATION OF THE DRAWINGS
The digitalisation was realised with the
objective of substituting the originals for consultation and reproduction
purposes, for print reproduction in up to 1:1 scale.
The
acquisition resolution was set at 300 PPI, with
a colour depth of 24 bit (8 bit per R-G-B channel).
In consideration of the dimensions of the originals (up to 180 cm
in length) and of the acquisition resolution, the ideal choice was
the use of digital cameras with digital scan backs, or equivalent
systems, equipped with a
tri-linear CCD sensor that
carries out the scanning of the focal plane in large format.
To avoid geometric distortion in the images taken, and to simplify
the maintenance of the parallel relationship between the focal plane
and original to be digitalised, the shots were taken from a zenith
position, while the application of two perpendicular
metric
scales and
target Kodak Color Separation
Guides and Gray Scale Q13 constituted the central point of the system
of control of metric and chromatic fidelity.
An illumination system with cold light, without IR or UV, was utilised.
The
master files were saved in non-compressed
TIFF
format with ICC colour profile incorporated. For purposes of consultation,
cataloguing, and monitor analysis
JPG images were
also produced from the master images, with lossy-type compression.
Requisites for digitalization:
- 300 PPI on the size of the original, without
use of montage
- Colour depth 24 bit RGB
- Parallel relationship between the focal plane
and the original
- Chromatic fidelity: juxtapostion of colour guides,
in colour and in grey scale
- Metric fidelity: juxtaposition of metric scales
in two directions