Graph of Intensity

Following the next steps you can construct the graph of the average value of the intensity per wavelength for specific areas of the painting. Bear in mind that you should have the normalized images in order to follow these steps.

Procedure

Step 1

Drag and drop the normalized images at ImageJ.

You will get something like that.

Note: The images should be from the smallest wavelength (bottom) to the largest wavelength (top windows). If the images are not in that order you can change their order by clicking on them one by one.

Step 2

In order to combine all these images to one "Stack" go: Image->Stacks->Images to Stack. A small window will pop up. Choose a name and click Ok.

You will get something like that. All images are now in one window. You can see all images by moving the horizontal bar at the bottom of the window.

Step 3

Now we will choose the type of calculations that we want to get. So go: Analyze->Set Measurements. A new window will pop up. Choose only the option "Mean gray value" and click Ok.

Step 4

Now we will choose the areas that we want to analyze.

Select again Analyze->Tools->ROI Manager. And in the small window will pop up. Select an area on the image (with the rectangle) and click "Add". You can add as many areas you want. You can see all areas together by selecting the "Show All" option on that window. You can delete an area by selecting on it and clicking the "Delete" button.

Step 5

Select: Measure->Multimeasure. On the new window select "Measure all xxx slices" and click Ok.

A new window with the results will pop up. The first column is the number of the image while the other columns are for the areas that you selected.

Step 6

You can get the data in order to draw the graph. Here we pasted the data to excel. We changed the numbers 1 to 5 with the wavelength and then we draw the graph for the data. You might have to change the dots to commas.

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