The set-up consists of a robotic, high-resolution color IP camera, as shown in Figure on the left. The camera is equipped with infrared led lights (12 of 850nm IR led), so that it is possible to record the image in total darkness. Color images captured by the camera have a resolution of 1920 pixels x 1080 pixels. 

The painting is placed in front of the camera. 

Various filters are inserted between the camera and the painting, which allow the selective passage of light through the camera lens.

So as the bandwidth of each filter to be determined, the school spectroscope in combination with data from CCD spectrograph were used, as shown in the Figure on the left. For example, this Figure refers to the red filter and it shows the spectral graph, as well as the photograph from the spectroscope (inset). 

The spectral bandwidth was then calculated from the degree of FWHM (Full Width Half Maximum) between λ1 = 631nm and λ2 = 755nm and thus the middle of the range, λmean, was determined at 693nm.

The same procedure was followed for the rest of the filters and the results are presented in Table 1 (on the left).

In order to reproduce what the camera records on the computer screen in a continuous video stream, we have created a program using a free software b4j (https://www.b4x.com/b4j.html), while the camera is connected via a router with the computer. With our program we can control the various functions of the camera (e.g. day-night mode, black and white display, etc.).

Images are converted to black and white (grayscale) for easy identification of areas that absorb radiation (black areas) and areas that reflect radiation (white areas).