## 2 Materials and Methods
### The Scientific Analyses
#### 2.2.1 High-Resolution Multiband Imaging  
The photographic system used was the Phase One XF with a modified IQ3 digital back (Trichromatic, 100 MP), with an extended spectral sensitivity ranging from 350 to 1000 nm and a [PERSON] 120 mm LS f/4.0 macro lens. The selection of the different spectral bands was made using different filters and light sources to choose the appropriate wavelength range for the investigations. In each of the considered bands, four images were acquired for each painting at a distance of 45 cm and merged to achieve a final image with  
Figure 1: Portraits of [PERSON] on the **left**, and [PERSON], on the **right**.  
spatial resolution of 50 px/mm. A scheme of the considered bands is shown in Figure 2, and it is detailed as follows.  
* Visible-reflected (Vis) Image: Two halogen lamps were used for the lighting (Dedolight DLHM4-300, dimmable 150 W with light condenser to reduce surface heating), and a UV-IR cut filter was used mounted on the lens of the camera.
* Ultraviolet-reflected (UVR) Image: Two 3 W 365 nm LED lights were used in a completely darkened room, combined with a 380 nm short-pass filter mounted on the camera lens to acquire the UV reflected by the painting surface.
* Ultraviolet false color (UVFC) Image: Vis and UVR image were combined using the blue and green channel of the Vis image, shifted, respectively, to the green and red channels of the UVFC image, and the UVR image was substituted in the blue channel.
* Ultraviolet-induced fluorescence (UVIF): Two 3 W 365 nm LED lights were used in a completely darkened room combined with a 418 nm long-pass filter mounted on the camera lens to acquire the Vis fluorescence emitted by the painting surface.
* Infrared false color (IRFC) Image: Vis and NIR image were combined using the green and red channel of the Vis image, shifted, respectively, to the blue and green channel of the IRFC image, and the NIR image was substituted in the red channel.
* Near infrared (NIR) reflectography: Two halogen lamps were used for the lighting (Dedolight DLHM4-300, with light condenser to reduce surface heating), combined with a 850 nm long pass filter mounted on the lens of the camera.
* ShortWave infrared (SWIR) reflectography: A spherical scanning system [19; 20] was used as in previous scientific campaign [16; 17; 18], it is based on an InGaAs camera (Xenics Xeva 1.7-640, 640 \(\times\) 512 elements, spectral sensitivity: 1000-1700 nm) mounted on a spherical motorized head, with a linear stage for the refocusing. A total of 360 images for each painting were acquired and merged to obtain a final image with a spatial resolution of 50 px/mm. Two halogen lamps were used for the lighting (Dedolight DLHM4-300, with light condenser to reduce surface heating).
* Visible microscopic imaging: A digital optical microscope AM4013 MZ with polarizing filter (5 MP, 50\(\times\) and 220\(\times\) magnification) was used to obtain microscopy images in the visible range. This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, and the experimental conclusions that can be drawn.  
Figure 2: Portrait of [PERSON], sequence of multiband imaging in the visible (Vis), reflected ultraviolet (UVR), ultraviolet false color (UVFC), UV-induced visible fluorescence (UVIF), false color infrared (IRFC), infrared between 850 and 1000 nm (NIR), and infrared between 1000 and 1700 nm (SWIR).