image processing of a Raphael's portrait of Leonardo
Amelia Carolina Sparavigna
Dipartimento di Fisica, Politecnico di Torino
one of his paintings, the School of Athens, Raphael is depicting
Leonardo da Vinci as the philosopher Plato.
Some image processing tools can help us in comparing this portrait
with two Leonardo’s portraits, considered as self-portraits.
"Scuola di Atene" is one of the most famous paintings
by Raphael, the Italian Renaissance artist. Painted between 1510
and 1511, this fresco decorates the wall of one of the rooms, the
"Stanza della Segnatura", in the Apostolic Palaces of
Vatican. The great Greek philosophers are represented inside a classic
architecture. At the central position of this masterpiece, we see
two philosophers, Plato on the left and Aristotle, his student,
on the right. Plato is shown as a wise-looking man (see Fig.1).
It is believed that Raphael based the Plato's face on the features
of Leonardo da Vinci . The two artists probably had established
a direct interaction when Raphael spent a period of his life in
Florence, perhaps from about 1504 to 1508 [2-4]. Leonardo da Vinci
returned to Florence from 1500 to 1506: therefore, if the image
of Plato is a portrait of Leonardo, this means that Raphael depicted
him when Leonardo was 52 or 54 year old. There is a portrait in
red chalk, dated approximately 1510 and held at the Biblioteca Reale
of Turin, which is widely accepted as a self-portrait of Leonardo
da Vinci. It is thought that Leonardo drew this self-portrait
at the age of 58 or 60 (see Fig.2).
Leonardo’s portrait in red chalk (dated approx.
5 tells that this wellknown drawing is not universally accepted
as a self-portrait, because the depicted face appears to be quite
old, suggesting that Leonardo represented his father or grandfather.
Another possibility is that Leonardo altered himself, in order that
Raphael might use it for his Plato. However, Plato does not look
so old in the painting by Raphael. In any case, let us try to find
some matching points between the portraits, that of the man in red
chalk (Fig.2) - let us call it, from now on, the self-portrait in
red chalk – and the image of Plato (Fig.1) that Raphael had
depicted in his fresco. To match the two faces, the image processing
is fundamental: in particular, we will use another Leonardo's portrait
merged with the self-portrait in red chalk. This portrait is a drawing
of the Codex on the Flight of Birds, which Leonardo had partially
hidden by his writing, as shown in Fig3, left panel.
A page of the Codex on the Flight of Birds contains
a Leonardo’s portrait.
Using a digital restoration that removes the writing, the
sketch of detail of a page of the
Leonardo da Vinci's "Codex
of the Flight of Birds"
to Carlo Pedretti, an Italian historian expert on the life and works
of Leonardo, this is a selfportrait [6,7] made when the artist was
young. The codex dated approximately 1505, but the portrait is older
for sure: Leonardo recycled the paper for the composition of the
Codex. To use this portrait it is necessary to remove the written
text. Carlo Pedretti was the first to suggest a “restoration”
of this drawing , of course not of the real page of the Codex,
but made on a photographic plate. The result that Pedretti obtained
in 1975, with a negativepositive photographic procedure, was quite
it was just in 2009 that the portrait became popular because of
an Italian scientific journalist, Piero Angela, that presented a
digital restoration of this portrait [8,9], that is, a restoration
of the corresponding digital image. In 2009, I have proposed a simple
approach that uses an iterative procedure based on thresholding
and interpolation with nearest neighbouring pixels [10,11]. Recently,
I proposed a further processing with a wavelet-filtering program,
Iris [12-14]: the result is shown in Fig.3, right panel. According
to Pedretti, this is the young Leonardo da Vinci selfportrait. For
any comparison with the Raphael’s portrait, we have to complete
this image, since the artist abandoned it unfinished. We use another
processing tool, the GIMP , for this purpose. Using GIMP, we
can add this drawing of the young man to the self-portrait in red
chalk of the old man. The result is given in Fig.4: besides showing
that the two faces have the same relative distances of eyes, nose
and mouth, this portrait makes the old Leonardo look younger.
Using GIMP  we can add the portrait of the young
man (Fig.3, right)
to the selfportrait in red chalk (Fig.2) of the old man.
On the right, the Raphael painting and on the left,
the result of a merging
of two Leonardo’s drawings
Figure 5 we have the two images, the Raphael painting on the right
and the result of merging the two Leonardo’s drawings on the
left, shown side by side. Let me remark that we are looking at two
images obtained from originals created by artists who used different
techniques and a different rendering of the head position. Moreover,
there is another fact, which is in my opinion quite important, that
the two portraits are showing a distinct side of the face. And we
know very well that the two sides are not equal and that the existing
small differences create the "good" and "bad"
side of our faces . Let us remember that for all the living
creatures, the bilateral symmetry  of the body is an approximate
symmetry: the two halves, left and right, of the body and then of
the face, are not perfectly symmetrical. The symmetry of human faces
is a subject of several studies.
researchers are supporting the idea that more symmetry means more
beauty and freedom from diseases [18-20]. On the other hand, a face,
which is too symmetric, gives the impression of being unnatural
. The fact that the two sides are different is quite relevant
if we are comparing a self-portrait with a portrait, because we
must be sure to compare the same side of the face. For the explanation,
let me use Fig.6. Let us consider two canvasses, having on them
a self-portrait and a portrait, with the head depicted in the same
position, the two paintings are showing a different side of the
face. When the artist is depicting a self-portrait, he is looking
at the face in a mirror.
it is another artist depicting the portrait, he is looking at the
face directly. For this reason, if the face on the canvas has the
same position, the depicted sides turn out to be different. Therefore,
if the left image of Fig.5 is a self-portrait and the right image
is a portrait, it is necessary to reflect one of then, to point
out that we are seeing different sides. I decided to change the
Raphael’s image, with a reflection and a small rotation using
GIMP. Moreover, I converted the colours in grey tones, to avoid
the vision of different hues.
Let us consider two canvasses, having on them a self-portrait
and a portrait
respectively, with the head depicted in the same position.
The side of the face is different.
When an artist is depicting a self-portrait, he is looking
at the face in a mirror. Assuming the position of the head
as above, the self-portrait is showing the left side of the
face. In the case that it is another artist depicting the
portrait, he is looking at the face directly, and then the
side depicted is the right one.
Is this the same person?
gives the result. Is the figure showing the same person? I guess
that there is this possibility, but further studies are necessary.
Let me then avoid a direct answer and just write some conclusions.
Using the image processing we had compared portraits having quite
different origins. This is telling that several processing tools,
some of them freely available, can help in the study of history
what concerns the specific case, it seems from Fig.7, that the structure
of the two faces, in particular of nose and cheekbones, is quite
similar. We can also see that one of the eyes is a little bit larger
in both images. According on the previous discussion on portrait
and self-portrait (Fig.6), I tend to consider the Raphael’s
Plato based on a direct interaction between Raphael and Leonardo,
when Raphael was in Florence, and then on a previous portrait or
drawing that Raphael made of Leonardo.
1. Raffaello, presentato da Mchele Prisco, Milano,
Rizzoli Editore, 1966; Raffaello Sanzio, presentato da M.G. Ciardi
Dupré, Milano, Fratelli Fabbri Editore, 1963.
2. Cecil Gould, The Sixteenth Century Italian Schools, National
Gallery Catalogues, London 1975; Henry Strachey, Raphael, G. Bell
and Sons, London, 1911.
3. Raphael, http://en.wikipedia.org/wiki/Raphael,
4. The School of Athens, http://en.wikipedia.org/wiki/The_School_of_Athens
5. Cultural depictions of Leonardo da Vinci, http://en.wikipedia.org/wiki/Cultural_depictions_of_Leonardo_da_Vinci
6. E. Crispino, C. Pedretti, C. Frost, Leonardo: Art and Science,
7. C. Pedretti, Disegni di Leonardo da Vinci e della sua scuola
alla Biblioteca Reale di Torino, Giunti Barbera, Firenze, 1975;
C. Pedretti, A Chronology of Leonardo Da Vinci's Architectural Studies
after 1500, E. Droz, Geneva, 1962.
8. ANSA.it - News in English - Leonardo self- portrait 'discovered',
2009 and also BBC NEWS Europe - 'Early Leonardo portrait' found,
10. Amelia Carolina Sparavigna, 2009, The Digital Restoration of
Da Vinci's Sketches, http://arxiv.org/abs/0903.1448
11. Amelia Carolina Sparavigna, 2009, Digital Restoration of Ancient
12. Amelia Carolina Sparavigna, 2011, A self-portrait of young Leonardo,
13. Iris © 1999-2010, Christian Buil, http://www.astrosurf.com/buil/us/iris/iris.htm
14. Amelia Carolina Sparavigna, 2009, Enhancing the Google imagery
using a wavelet filter, http://arxiv.org/abs/1009.1590
15. GIMP © 2001-2011, http://www.gimp.org/
16. I have read on the Glamour Magazine about a simple experiment
by P. Gugliemetti, Do You Have A Good Side And Bad Side Of Your
Face?, 11-13-2008. The author writes "At a party over the summer,
I mentioned to someone how I have a good side and bad side, and
she thought I was just being dramatic. So I had her take a photo
of each side and we showed the shots to random people in the room,
asking them to vote on which side was my prettier one. Every single
person voted right! Then we tried this on other people, lining them
up one-byone against a white wall, shooting their sides, and having
people vote. Only a couple had equally attractive sides."
17. Bilateral symmetry of a body means that there exists a plane
which is dividing the body into two mirror image halves. An operation
of reflection shows that the two halves coincide.
18. G. Rhodes and L.A. Zebrowitz, Facial Attractiveness - Evolutionary,
Cognitive, and Social Perspectives. Ablex. ISBN 1567506364, 2002
19. R.J. Edler, Journal of Orthodontics Vol.28(2), pag.159, 2001
20. K. Grammer and R. Thornhill, Journal of Comparative Psychology,
Vol. 108, pag.233, 1994.
21. R. Kowner, Journal of Experimental Psychology: Human Perception
and Performance, Vol.22, pag.662, 1996.