The beauty of paintings

The question I had in a childhood about what elements of a picture influence its evaluation became my research theme.

When starting this research, I found that "Beauty" is quite tricky concept.
"Beauty" is dealt with in various fields such as philosophy, mathematics, psychology, neuro-aesthetics, art and so on. 

 
For example, just to raise a few, in aesthetics, a branch of philosophy, "beauty includes ugliness."
In mathematics, the American mathematician Birkhoff defined the formula of beauty called 'aesthetic measure' as beauty = complexity/order.
In psychology, "pleasantness, novelty, and arousal are the factors".
Neuro-aesthetics says that "the orbitofrontal cortex activates when we see beautiful things".
According to one professor who graduated from Tokyo University of the Arts, "Beauty is a matter of color and light."
For them, "beauty" is a theme that they will spend all their lives exploring, and it is not something that can be defined in the first place.
As a matter of fact, he explicitly refused to discuss beauty with me. For him, a predetermined range of "beauty" was unacceptable.

I strongly realized that different standpoints have different ways of thinking.

Thus, "beauty" is being explored from so many different angles.  It is, just like a deep swamp.
If we do not limit the subject of our research to some extent, what kind of "beauty" we are researching, we will be trapped in this deep quagmire.
Thus, I decided to focus my research on paintings, ukiyoe among them, and limited periods and works within those paintings.

As a feature of the research, we decided to take a computational approach to "beauty", so we chose Ukiyo-e as a painting that fulfills the following conditions: it is not an abstract painting, has clear lines, does not mainly depict people or faces, which are cognitively special objects, and is recognized as a masterpiece in its category.