Profilocolore for Cultural Heritage
Profilocolore has developed, for the Cultural Heritage world, a number of non-invasive diagnostic tools that allow in-depth analysis of artworks, such as paintings and frescoes, with an innovative scientific methodology, extremely precise and repeatable yet simple to perform. The whole analysis process can be divided into three stages: 1) acquisition of the images, 2) calibration and conversion of the digital images into into imaging measurements, 3) post-processing, analysis, aggregation, classification, storing in DB and integration of results.
1) The acquisition takes place through high level digital cameras, suitably modified to reach a sensitivity from ultraviolet up to infrared, in particular in the 300-1000 nanometer range (UV-VIS-NIR). Beside the subject to be analyzed, radiometric, colorimetric and photometric references are positioned together with the subject under analysis. The scene is lit by a Nikon flashes, these too modified for a full UV-VIS-NIR emission band.
To obtain a multispectral imaging only two photos are required to be shot, using the PFCL-A and PFCL-B filters.
Eventually, a third image can be acquired to evaluate the fluorescence, with flashes equipped with PFCL_UV_Fluo filters and camera equippend with a PFCL UV-IR cut filter and a PFCL-A filter, coupled together, that make the camera to work as a standard colour camera.
The camera can be directly operated, as in normal photography, or can be completely controlled with the PickCamera Profilocolore software. This software not only controls all the functions of the camera through an USB interface, but it als implements the full image acquisition protocol, controlling the corretness of te acquisition and even automaticaly setting some critical parameters like the exposure and the autofocus.
Any other kind of further images can be acquired , like raking light, narrow bandpass filtered images, or even other kind of fluorescence images (UV to NIR, VIS to NIR).
2) The calibration is done with SpectraPick that is an highly automated and optimized software, based on artificial intelligence, that, starting from radiometric references in the scene setup, builds all the mathematics needed to convert input images in real radiometric and colorimetric measurements.
From this process we obtain monochromatic contrast images corresponding to 7 bands centered at 350, 450, 550, 650, 750, 850 and 950 nanometers, with a radiometric precision of over 95%, and a CIELAB color image, (exportable in AdobeRGB or any other colour space), with a colourimetric accuracy less than of dE2000=2.
All these measurements are available at a spatial resolution that depends on the camera and dimension of the acquired surface. For example using a Nikon D850FR camera, that is equipped with a 8256 x 5504 pixels sensor, and acquiring a painting of 1×1.5 meters, we obtain a spatial resolution of 25 pixel per square millimeter.
High spatial resolution has little importance for homogeneous surfaces, but in most of real applications, being able of recording differences in colour and spectra between very little adjacent areas can be of extreme importance to catch, distinguish and discover the thinnest details.
One of the features of SpectraPick is to offer the user all the tools to integrate imaging data coming from other kind of sensors, even from scan based measurements (like XRF or Raman). Whatever resolution is the original data to integrate, SpectraPick automatically samples and align it to make it compatible to all the colorimetric and radiometric images.
3) Post-processing of the calibrated and external integrated data can be performed using PickViewer, full of functions, part of which extremely useful for cultural heritage. This tool accepts any kind of images, provided they have aligned as SpectraPick does, and integrates them to run a wide set of analysis functions, from multispectral and colorimetric point and area reading, to Principle Component Analysis, Features Clustering, Search of Spectra inside images, Mapping of pigments, normalized comparision among spectra and colours, storage of spectral into the embedded DataBase.
Sometimes, surface conditions and environment constrains let us to struggle with reflections, and reflections prevent any kind of investigations where they happen.
Profilocolore developped and effective pre-processing procedure and the PickShine software tool that combined overcome the goal of removing reflections and are a real surface characteristics analysis instrument. The main result is to obtain a radiometric correct reflections free image of the surface under investigation, and as side effect results it provides an only relfection image that immediately gives the feeling of the nature of the surface micro roughness.