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Lerma 
3. IMAGE ACQUISITION 
The archaeological cave was photographed with a standard 35 mm camera using both colour and near-infrared B&W films (Fig. 1). 
In order to bring out pigments, the stone wall was again photographed with colour film after moistening. 
Fig. 1: Original images: visible (a), near-infrared (b) and visible after moistening (c) 
Each visible photograph was scanned with a resolution of 600 dpi and a quantization level of 24 bits/pixel; the near-infrared 
photograph was scanned with the same resolution and 8 bits/pixel. 
Warping was required because images were neither taken with the same camera nor taken from the same location. Besides, the 
images needed to be georeferenced to cave in order to get useful, profitable and real data from them (Fig 2). After warping and 
resampling, the multiband set had in total seven spectral bands: three visible (r,g,b), one near-infrared and three additional visible 
bands (after moistening). 
Fig. 2: Images warped and extracted: (a) visible, (b) near-infrared, (c) visible after moistening