Art collectors spend millions to buy masterpieces, but the masterpiece
they buy today could prove to be virtually worthless tomorrow if
they aren't careful. Now, researchers at Dartmouth University say
they have developed a technique that uses the power of a computer
to help collectors determine whether the investment they've made
is a sound one.
The technique begins with a digital photograph of a painting,
drawing or print that captures the subtle texture and brushstrokes
of the artist.
"It's very, very high resolution. Tens of thousands
of pixels by tens of thousands of pixels," says Hany Farid who
heads the team that did the study at Dartmouth. He says the
computer then analyzes the image in the same way similar programs
have analyzed literature to determine authorship.
"When people were trying to authenticate Shakespeare's sonnets,
they looked at a previous body of work believed to belong to him
and they compared statistically that body with the works in question," he
explains. "The statistical measurements there are word distribution,
length of sentences, punctuation, things of that sort. We
do a similar thing. It's just that the statistics are now
in respect to images."
Mr. Farid says
the technique uses the same type of technology that compresses
information in a photograph so it takes
up less memory. He refers to a study done using a painting
attributed to Italian Renaissance artist Pietro Perugino, which
experts believe was completed with help from some of his students.
"Let's consider the master and the way he may paint," he adds. "Probably
very smooth brushstrokes, very consistent, very delicate, very
elegant lines. And when the imitators try to imitate, probably
a little bit jerky, because we know that when you try to mimic
somebody's actions it never comes out smooth. Now let's imagine
compressing the image of the master. Probably we'll have
a lot of redundancy because of the consistency in which it's painted. Whereas
the student is less consistent, so there are less redundancies
and it will not compress into as small a file."
Since different portions of the painting compressed to different-sized
files, Hany Farid and his team of Dartmouth researchers determined
that different artists painted them.
artists are not always consistent. They have been known to radically
styles. Take the 19th-century master,
Vincent Van Gogh, for example, whose brushwork changed dramatically
from his early, dark Dutch paintings, to the colorful landscapes
he did in his final years in southern France. Hany Farid
says the technique he and his team developed to analyze art is
only good within a narrow time period. He emphasizes that
it is only a tool, one that still requires an expert's reading
of the data.
"This does not tell you who did what," he explains. "It
simply tells you about consistency. We say we believe there
are many hands present in this painting. And the art historian
may come in and say, 'This figure on the left. This is the
best quality, so this probably belonged to the master.'"
to analyzing the Perugino painting, Mr. Farid says the technology
applied to thirteen drawings to determine
which were done by Flemish artist Pieter Bruegel and which were
imitations. Their conclusions were consistent with those
of art historians. The Dartmouth team plans to do more tests over
the next few years, with hopes that the technology will eventually
become a standard authentication tool for the worldwide art collection