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Multispectral Technical Specifications

The dynamic reconstruction of the color

    • 13 mesurements from UV to IR, before reconstruction of the image at 240 millions true pixels

    • The dynamic reconstruction of color requires for each pixel the acquisition of spectral reflectance curves from the 13 multispectral image capture.

    • Thus 260 million curves of spectral reflectance are rebuilt dynamically to calculate the color of this pixel for one illuminant of which we know the curve of spectral emission.

     

 A Primer on Multispectral Digitization

  • Interaction of the pictorial layer with the incidental light.
    • The rays of light coming a light source illuminating a painting are absorbed and diffused by the pictorial layer.
    • The part not absorbed by the pictorial matter is what is considered.
    • The light reflected by each element of the pictorial layer can be recorded on a sensitive plate (photography)  or detected by solid detectors sensitive to the light or punctually measured with a spectro-colorimeter, a goniophotometer or a multispectral camera in order to build the curve of spectral reflectance of colored surface.
    • The light, generally seen in a diffuse way, also comprises a part known as specular which corresponds to the brightnesses due to varnishes and the gold sheets.
    • A pictorial layer is a heterogeneous medium comprising a binder in which are dispersed diffusing particles called pigments. It can be covered with a varnish (transparent or slightly absorbent).  Lastly, the pictorial layer rests on a substrate that can be diffusing (wood or fabric covered with a preparation) or reflective (metal bottom)
       
  • The light is concentrated by an elliptical mirror and projected as a line on the painting.
    • Very high intensity illumination : greater than 100,000 lumens
    • Two lines of light from the right and the left projectors are synchronized with the CCD sensor of Jumboscan in order to use the maximum of light intensity.
    • Spatial homogeneity of illumination
    • The painting receives very insignificant energy from the light (less than 50lux/hour) and guarantees its care and preservation .
    • Minimized total light exposure
    • No emission in the UV(B & A) and no heat
    • Continuous light spectrum emission
    • Non distortion of the colors.

 

 



    The Basics

    • The multispectral camera, developed within the framework of the European project CRISATEL, makes it possible to measure simultaneously 240 to 360 million pixel points of the pictorial layer.  Lumiere Technolgy ‘s digitization system can record the specifics of each pixel down to 30 microns, where as other scanning techniques operate, at best, on the level of a few millimeters.

    • Thirteen filters located between the optics and sensors make it possible to record layers sequentially exposing them to both ultra violet and infra red wave bands. From 380 to 1050 nanometers.

    • The resulting data, layer by layer, and pixel by pixel, is then processed by Lumiere Technology’s patented software system, providing an end result that is scientifically superior to any other system available today.