Multispectral Image Analysis for Art. MultiSpec

This post introduces MultiSpec,the Multispectral Image Data Analysis software that I use. It’s free and pretty easy to use. On their website you’ll find tutorials and examples to learn and master it, so, I’ll just give here a very simple example of its application for examination of art. Just to let you see how neat it is. Then it’s up to you figure out how to apply it for your specific art examination tasks.

The Whites’ experiment

I painted a piece of paper with the four most common white pigments: lead white, lithopone, titanium white and zinc white. Wouldn’t be nice, I thought, to be able to differentiate among them just using a multispectral imaging camera? On the left I painted one spot for each pigment. These would be the “training areas” for the software. I need to tell MultiSpec what is lead white, lithpone and so on. On the right I painted a line and some letters. This is the area where hopefully MultiSpec would be able to identify the pigments.

Visible Light Photo of the test paper with four white pigments.

 

MultiSpec screenshot. Visible photo with training areas indicated in Multispec. four areas for the pigments and one for the paper.

I ran MultiSpec and the result is pretty disappointing. The software cannot identify the pigments just using the visible image. Though, this is what I would have expected, since the pigments look pretty the same in the visible photo.

 

MultiSpec tries to identify the pigments using just the visible image and it fails.

I can add now to the visible image the other multispectral images, UV Fluorescence (3 channels), UV Reflected (1 channel), Infrared (1 channel) and logically link them into a 8-channels multispectral file which I can feed to MultiSpec.

 

Multispectral images of the test paper painted with 4 white pigments.

I repeated the same training procedures. MultiSpec can now look at the behavior of those pigments in 8 channels rather than just the 3 visible channels. So, I did expect it to be more successful and, indeed, It was able to identify zinc white and titanium white while could not differentiate among lead white and lithopone.

 

MultiSpec can identify zinc white and titanium white using the multispectral 8 channels image file.

This is actually what I was expecting. My flowchart for identifying white pigments shows clearly that UVR and UVF are sufficient to differentiate zinc white and titanium white from the other two whites, lead white and lithopone.

White pigments Identification Flowchart.