very happy to have the After Thoughts of Falco and Graves (in blue)
as they clarify some issues and highlight the difficulties and inconsistencies
in the optical theory. It many cases it seems to be the first time
they've entertained alternate explanations for several phenomena
(at least publicly), and for that we can be grateful. Moreover,
while it appears that they would like us not to consider the material
given by Mr. Hockney himself -- the creator of the theory, author
of its book, and explicit titular reason for the New York symposium
-- his views must and will also be confronted. That's what I was
asked to do for the symposium, and what I will continue to do.
David Stork's objections
Stork's arguments against our evidence are scattered throughout
his fourteen web pages, they reduce to: 1) there is no historical
documentation of the existence of appropriate mirrors and lenses
during the early Renaissance; 2) artists had sufficient talent
that they wouldn't have needed to use lenses anyway; and 3)
it would have required an impossible number of candles to provide
sufficient illumination to use such lenses. We show that 1)
documentation certainly does exist that demonstrates appropriate
mirrors and lenses were being produced and used as imaging devices
as early as the 13th century; 2) the question of whether or
not artists had the talent to paint without the aid of lenses
is a logical red herring, unrelated to evaluating the evidence
we have presented that, irrespective of their skill level, certain
of them indeed did use such lenses; and 3), as we clearly stated
in New York, they didn't use candles, they used sunlight.
No. There are several other problems
I raised that do not reduce to the above three classes and Falco
and Graves do not answer them, for instance Why the embarrassing
lack of inverted brushstrokes (even in underpaintings) in Renaissance
art? What about alternate explanations? Do they think the first
is "unrelated" to the question of whether paintings were
at least partially completed upside-down? These problems for the
Hockney theory, and others not answered by Falco and Graves, as
well as rebuttals to their points will be presented below.
We have organized
what follows according to the headings on the fourteen web pages
of Stork's discussion. However, since many of the points Stork
emphasizes are unrelated to our evidence for the use of lenses,
we have not addressed all of his points that are incorrect or
I've seen many
students in the National Gallery and elsewhere copying masterpieces
with great fidelity. .
Here Stork invokes
an alternative hypothesis ("artistic genius"), which
does not address the optical evidence we presented. Unfortunately,
as well as not addressing our evidence, his term "great
fidelity" is completely subjective, so cannot be tested
against any of our optical evidence. The correspondence of a
wealth of intricate features on the Albergati drawing and painting
are at a scale smaller than 1 mm (0.039"). An optical projection
using a simple version of what is now called an epidiascope
is the simplest way to achieve such accuracy.
First of all, nowhere do I invoke
the phrase "artistic genius," as their quotation marks
imply, or even that concept. On the contrary, I refer to "students"
and state that there are thousands of paintings done "optically"
-- hardly an appeal to "artistic genius." Under my title
Drafting Talent (not "Genius"), I touted a single individual,
a Texas police sketch artist... whom I suspect would be flattered
indeed to be associated with the term "artistic genius"
that Falco and Graves introduce into the discussion. Even for van
Eyck I refer only to his "own patient talent" and summarize
the whole discussion thus: "it seems plausible that van Eyck,
Leonardo, Caravaggio and other Renaissance painters had the requisite
talent." While Falco and Graves here and below may hope to
portray my position as somehow relying upon "artistic genius,"
and thus somehow extraordinary or implausible, the simple fact is
that I am not and never have. I don't need to.
Next, it is worth pointing out that
neither Hockney nor Falco and Graves themselves had put forth the
grid alternative to the optical explanation of the Albergati copy.
Why not? Are they that unaware of the history of technology of the
time? They ask "How else to account for the convergence except
by way of some sort of optical projection?" as if the answer
were self-evident. Do they hope their audiences will not bring up
alternatives? How can they make claims -- including claims for "proofs"!
-- without doing so?
Lorne Campbell, Research Curator
at the National Gallery, London, author of Fifteenth-century
Netherlandish art and van Eyck expert, claims that van Eyck
did the copy by eyeballing (pers. com. 2002). A 1-mm resolution
-- the thickness of a dime -- isn't particularly farfetched given
that an artist can measure and scale distances (without a grid)
and has his own source image in front of him, even if he's enlarging.
Regardless, as I wrote, eyeballing is not my favored explanation,
but neither can it be dismissed immediately, as Hockney and Falco
do. Falco and Graves complain that the eyeballing explanation was
not compared to the evidence, ignoring the fact that neither has
the optical method.
The epidiascope is by not the simplest
means to achieve this accuracy, and has never even been demonstrated
in this regard. In the Renaissance it required an expensive and
at best rare (but probably nonexistent) device along with strong
lighting and complicated setup. A grid construction is simpler and,
as I've demonstrated experimentally, gives more than enough accuracy.
our epidiascope explanation fails, and offers "an extremely
simple experiment" as proof: Place a notebook or paperback
book on a flat tabletop -- this will represent one of van Eyck's
image surfaces (paper or canvas). Now randomly "bump"
the notebook." Based on the fact a notebook would rotate
when bumped, but there is no relative rotation between the features
in the drawing and painting, he concludes the correspondence
of details "would be extremely unlikely in the Albergati
portraits according to the Hockney/Falco theory.
the simple experiment Stork proposes to support his view is
an experiment that does not reflect the likely situation of
the drawing and the painting both having been mounted on easels
of some sort. Obviously, bumping either easel would move it
horizontally with respect to the other, but would not result
in any rotation whatever between the two.
Falco and Graves are in error here.
Earlier I had considered an easel "explanation" but didn't
even mention it because it could not account for the data. Because
Falco and Graves cannot see this, it pays to show the contradictions
inherent in their hypothesis. In short, they ignore my central point
which was that, unfortunately for Hockney, Falco and Graves, there
are TWO "lucky" bumps -- one horizontal and one vertical.
Their new easel hypothesis may ensure that ONE bump is horizontal
(and yield no image rotation), but their hypothesis precludes an
orthogonal, vertical, bump (and no rotation) -- unless of course
they ask us to accept that van Eyck's canvas levitated above an
easel rail. (Incidentally, another ad hoc technique of moving the
canvas forward and backward would change the magnification and hence
cannot explain the vertical "bump.")
Furthermore, Falco and Graves conveniently
speak about the rotation but mention neither the ratio of distances
of the bumps, which is extremely unlikely in their ad hoc explanation,
nor the existence of the lines at the right of the image. And of
course their explanation relies at its heart upon complicated technology
for which there is no persuasive evidence (see below) while mine
relies on simple technology that was used at that period and indeed
Most importantly, they have stated
nothing to cast doubt upon my grid construction and experiment,
which remains the best explanation for the van Eyck images and is
in every way superior to their optical theory.
the third method for duplicating the Albergati portrait: pantographs.Leonardo
Stork is incorrect
in his belief that van Eyck could have used a pantograph in
1432. According to Martin Kemp, the pantograph was invented
by Christopher Scheiner in 1603, over 150 years after van Eyck
painted the Albergati portrait, and 84 years after Leonardo's
 Martin Kemp,
The Science of Art (Yale University Press, 1990). page 180.
This is quite surprising and welcome
indeed -- Falco and Graves are sounding like me: claiming that an
explanation is invalid because the required device wasn't yet invented.
GREAT! They rest their argument on Kemp's book. Did they ever bother
to try to look up in that book "epidiascope," or "mirror,
concave projection" or anything that would support their projection
hypothesis? There is nothing in Kemp's book or indeed any relevant
book I've seen that gives support to their epidiascope hypothesis
in particular or to mirror projection generally. How can they use
Kemp's book to discredit pantographs, when in fact it discredits
even more firmly their epidiascope hypothesis?
Of course, Falco and Graves cannot appeal to Kemp as an authority
if they choose which parts of Kemp they accept and which they reject.
To do so would be to undercut any appeal to Kemp's authority on
The simple fact is that the pantograph
was invented in 1603, long before the Dutch physicist Christian
Huygens (1629-1695) invented the precursor to the epidiascope. The
brilliant mathematician Leonard Euler was probably first to describe
projector for opaque objects in 1750-51 nearly a quarter millennium
after Falco and Graves claim it was used. Related technologies are
the megascope of J.A.C. Charles (France) of the late 18th-century,
the fantascope, which could also project slides; the episcope; Wunder
Camera and Aphengescope, all long long after the time Falco and
Graves claim such a system was in use. And if we want to talk about
the availability of the components of these devices, the wood sticks
of a pantograph were available to cave men tens of thousands of
years before the sophisticated concave mirror required for an epidiascope,
and the pantograph's parallelogram principle was known twenty-three
centuries ago, long before ray tracing in concave mirrors had even
been thought of. In short, the pantograph is far more plausible
than the mirror projection method, and, as I pointed out, the grid
construction is more plausible than either.
In arguing against the pantograph
because it hadn't been invented, Falco and Graves are -- unwittingly
-- arguing against their theory better than I ever could. Since
the long-focal length concave mirror hadn't been invented -- surely
not patented -- and there is no evidence that it was used for projections,
all their explanations based on it succumb to the dismissal they
serve to pantographs. Fortunately for me, I have an alternate explanation,
which I clearly and explicitly prefer. Unfortunately for Hockney
et al., they don't.
The explanation by grid construction
is in every way superior to an explanation resorting to optics.
The grid explanation relies on elementary technology known to be
used at the time, which in modern re-enactments gives correspondence
better than the originals, gives a natural explanation for the direction
of BOTH bumps AND their relative distances, and gives a principled
explanation for the vertical lines at the right. In contrast, the
optics explanation relies on complicated and at best rare devices
used in a way for which we have no corroborating textual or representational
evidence whatsoever, requiring bright lighting, which has never
been verified by re-enactments, can only explain BOTH bumps by appealing
to levitation, has no principled explanation for the relative distances
of the bumps, and has nothing to say about the vertical lines at
It is no wonder the promoters are
not eager to put forth alternatives to their optical theory. .
I understand that Christopher Tyler
will reply to this point in his After Thought.
prominently in Hockney's theory, yet this painting exposes numerous
awkward implications of the theory related to refocusing, moving
the canvas, and illumination.
inference of three "awkward implications" for "Supper
at Emmaus" comes from his misunderstanding of what is proposed.
An experiment based on this very painting was carried out in
Hockney's studio in May 2001. The results of that experiment,
in which Hockney used a refractive lens to assemble the painting
as a collage of separate elements according to the theory, were
entirely consistent with what the theory suggests for refocusing,
moving the canvas, and illumination.
As I stated in my piece, "I
am aware of just three modern demonstrations" and describe
them; of course I cannot comment upon experiments that have, to
my knowledge, not been revealed to the public. We look forward to
Mr. Hockney presenting his May 2001 results in sufficient detail
and clarity in a scholarly forum so that others can judge them,
including issues such as the consistency of viewpoints, direction
of brushstrokes, color fidelity, and much more. Until Hockney reveals
this evidence I'm afraid we'll have to withhold judgment on their
claim that the results "were entirely
consistent" with their theory. Regardless, knowledge
of simple optics ensures us that if Hockney had refocused on Peter's
right hand as he describes in his book, then he would have moved
the both the lens and the canvas six feet, an awkward and unlikely
had employed the methods of Hockney and Falco, how many candles
would he have needed?
We answered this
at the New York symposium, and the answer is the same now: none.
As we each stated then, direct sunlight is the likely source
of illumination, since direct sunlight has the necessary brightness.
There are numerous Renaissance paintings done by artificial
light, such as George de la Tour's evocative scenes...
One throws up one's hands in exasperation!
When I quote Mr. Hockney, the originator and driving force of the
theory and the titular reason for the symposium, when he wrote that
Caravaggio "...worked in dark rooms -- cellars -- very common
in those days... He used artificial lighting" and his supporters
respond instead "direct sunlight is the
likely source of illumination" one doesn't know whether
the proponents realize their blatant contradiction, or that they
think we won't see it, or what. At the very least, Falco and Graves
should take Mr. Hockney aside and tell him to stop misleading the
popular press. To wit: one august periodical known for penetrating
research and trenchant skeptical analysis, when interviewing and
lavishing praise upon Mr. Hockney and his bold theory, states that
Caravaggio "[w]orked in darkened cellars -- which you need
for the lens to work. Strong artificial lighting (ditto)" .
Regardless of such contradictions
on this central matter of illumination, their argument against the
historical record of Caravaggio's estate which contained a convex
mirror ("scudo a specchio" or shield mirror, almost surely
the one depicted in "The conversion of the Magdalene"
and completely useless for projections) and several candle holders,
his working methods that included at least at some periods a dark
cellar without sunlight, and so on -- reviewed over centuries by
art historians -- seems to be that it is incompatible with their
new theory. Caravaggio's biographer and rival G. P. Bellori wrote
in 1672: "He never showed any of his figures in open daylight,
but instead found a way to place them in the darkness of a closed
room, placing a lamp high so that the light would fall straight
down..." Joachim von Sandrart wrote in 1675: "He used
dark vaults or other shadowed rooms with one small light (liecht)
above, so that the light falling on the model made strong shadows
in the darkness..." In 1617-21 Giulio Mancini wrote 'A characteristic
of [Caravaggio's] school is lighting, from one source only, which
beams down without reflections, as would occur in a very dark room
with one window and the walls painted black, and thus with the light
very strong and the shadows very deep, they give powerful relief
to the painting, but in an unnatural way.' None of these support
the Falco (revised) hypothesis that Caravaggio worked under bright
Caravaggio lived in the Palazzo Madama, home of Francesco Maria
Del Monte. Del Monte's brother, Guidobaldo, wrote Perspectivae,
one of the most influential books on geometrical perspective in
the Renaissance' working methods in the Renaissance. But this book
says nothing about the mirror projection system which he would surely
have learned around Caravaggio, had it been used. Why? The unjustified
claim that Caravaggio used optics forces the proponents into the
extremely awkward conclusion that he worked under bright sunlight.
interpretation of the contents of paintings is very odd indeed.
There is no reason whatever to assume scenes were illuminated
by the sources of artificial light depicted within those scenes,
just as there is no reason to assume scenes containing dragons
were painted with dragons actually present.
|It's not odd at all that a painter
would best paint what he sees, or arrange his studio to appear
close to how he wants his final painting. Not odd at all, especially
in the Renaissance. It is very odd indeed that a painter would
try to make a painting look like it is night time when in fact
the scene is illuminated by bright sunlight, or would work with
very dim inverted images much of which are out of focus, or
would use an extremely rare (and probably nonexistent) technology
when he had done other methods, or had to constantly correct
for color (see below) -- all as arising in the Hockney/Falco
theory. Now THAT is passing odd! Hockney and Graves write: "There
is no reason whatever to assume scenes were illuminated by the
sources of artificial light depicted within those scenes"
but in fact there is, and every representational artist I know
(save possibly Mr. Hockney) would have chosen artificial illumination
had they wanted to produce the painting de la Tour gives us.
If de la Tour wanted to show light passing through the translucent
fingers of the girl, to show the proper shadows of the man's
left thumb and the wooden beam's left corner, to get the highlight
on St. Joseph's forehead, he would use the candle. Even the
slight irregularities, if any, can be explained by slight repositioning
the models during the execution and does not require two exposures
of sunlight. Arranging such "exposures" would be extremely
awkward, where bright sunlight comes from the left for one figure,
then must somehow come from the right for the other, all to
make the light appear as if it emanated from a point at the
candle! Mr. Hockney's suggestion that this painting was done
by sunlight is extremely implausible.
I think it pays to pause for a moment,
particularly for the artists reading these pieces who may be a bit
bewildered by technical talk of focal lengths and so on, to rely
on your eyes for a moment. I invite you to expand the de la Tour
painting, study it carefully for several minutes, all the time saying
to yourself "Hockney and Falco claim this painting was made
with the models illuminated by bright sunlight" as described
on page 128 of Secret Knowledge. For a few minutes, rely
on your own visual intelligence and see if you agree.
 "Have you seen the new David
Hockney?" by Andrew Marr, pp. 44-50, High Life (October, 2001)
[British Airways inflight magazine]
No comment is
necessary on this section.
I'm glad it is now clear to Falco
and indeed everyone that my criticisms both at the symposium and
on this website of the Arnolfini mirror have always been on its
focal length and thus the size of the sphere from which it was cut
(according to Mr. Hockney) -- not the areal size of the mirror face
I searched through
other contemporary paintings for depictions of mirrors or even
glass spheres that might be consistent with the long focal lengths
required by the Hockney/Falco theory, but found none. There
is no record that such "burning mirrors" were of sufficient
quality or sufficiently long focal lengths to be used as they
propose, or that we have little or no persuasive evidence they
were used for any imaging tasks (see below).
Here again Stork
is completely wrong. Not only is there written evidence that
appropriate concave mirrors existed at the time, but also that
they were in use for imaging tasks (see, for example, Section
2 of Reference 1). There also is compelling visual evidence
that Stork is equally unaware of. For example, Tomasso da Modena's
1352 paintings of "Isnardo of Vicenza"[Fig. 2] and
of "St. Jerome"[Fig. 3] both show gently curved (i.e.,
long focal length) mirrors. As for evidence they were used for
imaging tasks, Robert Gibbs writes on page 85 of his book
"Isnardo da Vicenza is preparing his office; there is a
reading glass (an enlarging-concave-mirror) on the shelf behind
him." Further, in a footnote to that sentence, Gibbs explains
"Mirrors, despite their inconvenient habit of reversing
the text, were used alongside lenses to enlarge small and faded
handwriting." Gibbs continues in his footnote "The
use of mirrors for reading continued into the sixteenth century,
and the second (not the first) representation, of a variant
type set in a leather horn rather than on a fixed metal stand,
appears on St. Jerome's shelf..."
 Robert Gibbs,
Tomaso da Modena (Cambridge University Press, 1989).
 nb. In fact,
when properly oriented, concave mirrors magnify the text without
Hockney and Graves are quite correct
that I was unaware of the Tomaso da Modena's two paintings. But
I am especially grateful that they have managed to uncover these
paintings because -- contrary to their claim -- the mirrors depicted
in them do not reveal that they have the long focal lengths demanded
by the Hockney/Falco theory, and the text does not support the use
in the form required by the optical theory.
First, the issue of focal length.
The focal length of the mirror in "The Blessed Pietro Isnardo
of Vincenza" is difficult to determine, but upon very close
inspection, a small highlight is visible. More relevant is a curved
line at the right, presumably the reflection of the vertical edge
of the shelf case. I estimate the diameter of the mirror face to
be about 6 cm, and from the curved line and placement of the edge
that its focal length is short -- roughly 4 cm. Admittedly, there
are uncertainties, but there is no justification for claiming that
the focal length is long (50 cm, say), such as needed for the Hockney/Falco
theory. Likewise, the mirror in the conical holder in "St.
Jerome" is hard to determine, but there's no evidence that
it has a long focal length especially given the short focal length
estimated for Pietro Isnardo's mirror. Further, the short-focal
length mirror would give greater magnification in its reading mirror
use; Pietro Isnardo wouldn't have even wanted a long-focal length
mirror if he had one . Falco and Graves are wrong to state that
they have evidence that "appropriate
concave mirrors existed at the time." The whole issue
has always been long-focal length mirrors (I've conceded short focal
length mirrors, as for burning for instance), and this new evidence
fails here too.
Second, the question of evidence
of imaging tasks. Falco and Graves are right that they have uncovered
textual evidence of an imaging task. But it is important that readers
understand some more optics. Up to now, we have nearly always spoken
about the image in a concave mirror to be the image projected by
that mirror, as in the Hockney/Falco theory. As mentioned many times,
this projected image is inverted or upside-down. We must now note
that this image is called "real" because light actually
passes through the image -- after all, that's what illuminates the
canvas. But a concave mirror can also produce a different sort of
image -- a "virtual image" -- such as when you look at
your nose in a makeup or shaving mirror. Here the image is instead
erect or rightside up, and is on the other side of the mirror. This
image is called "virtual" because no light actually passes
through the position of the image; the light leaves the mirror as
if it had come from the image. Such a virtual image cannot illuminate
a canvas in the way the real inverted image can. (Incidentally,
your image in a plane bathroom mirror is similarly virtual, and
of course erect.) When I wrote that we have little or no persuasive
evidence that concave mirrors were used for any imaging tasks, the
context was for real images, as in the Hockney/Falco theory, not
the virtual ones in the Tomaso da Modena paintings. Let me clarify
my statement then to account for the context in which it was written:
"We have little or no persuasive evidence that long-focal length
concave mirrors were used for imaging any real inverted images as
required by the Hockney/Falco theory."
Gibbs wrote: "Mirrors,
despite their inconvenient habit of reversing the text..."
and this is crucial. It proves that the concave mirror was being
used much as a shaving or makeup mirror, and that the monk was seeing
a virtual image behind the mirror (which reverses left-to-right),
not the projected real inverted image of the Hockney/Falco theory
(which does not). While Falco and Graves give a nb on the topic,
there is no evidence the monks figured out the major task of how
to project an image central to the optical theory, or that the quality
of the mirror would have supported such a projection. After all,
I surmise Mr. Hockney had spent many hours with shaving mirrors
and only learned about their projection abilities from a PhD in
physics in the 21st century when Hockney was into his 60s. Falco
and Graves provide no evidence anyone in the Renaissance or before,
including Pietro Isnardo, did.
The bigger question remains unanswered:
WHY, after years of research by numerous historians of optics, technology
and art, is it so hard to find such evidence that long-focal length
concave mirrors existed, much less that they were used to project
a real inverted image (or of course that such images were traced
or painted over)? I'm happy to join the chorus refuting Mr. Hockney's
claims about the Inquisition or trade secrets on this topic, but
I'd like to know if Falco and Graves agree with him, or instead
have another explanation. Although I urge Falco et al to comb the
historical records, unfortunately for them the more anyone finds
evidence such as they present above, the more the silence on appropriate
mirrors and their projection use becomes deafening. This is because
such new evidence makes more and more implausible at every turn
that there was a conspiracy, that historians somehow overlooked
the evidence, or that the Inquisition (Isnardo was a Dominican monk,
after all) was suppressing such a conspiracy and leaving us no evidence
in this regard. In my piece I listed several dozen optical instruments
uncovered by historians of optics, and in light of these Hockney
et al give us no reasonable explanation for the lack of corroboratory
evidence of long-focal length concave mirrors and their use in projecting
real inverted images.
Since they don't address it, I'll
assume Falco and Graves agree with my refutation of Mr. Hockney's
claim that the convex Arnolfini mirror could have been used in the
making of the painting itself. The elementary fact is that it could
not and I very much hope that Hockney and Falco will refrain from
claiming otherwise in their public and other venues, such as this
month's Smithsonian magazine which reads "Had Jan van Eyck
turned over the convex mirror hanging on the wall in his Arnolfini
Wedding, he would have held an optical tool suitable for creating
the meticulous detail found there" .
The simple fact remains that STILL
no one has shown corroboratory evidence that long-focal length concave
mirrors existed in fifteenth-century Europe, or that anyone had
ever seen the real, inverted image projected by such a mirror demanded
by the Hockney/Falco theory. Mr. Hockney surely doesn't provide
such evidence in the "Textual evidence" section Secret
Knowledge and neither do Falco and Graves here. My summary from
the conference paper website stands unaltered, and indeed strengthened
because after further effort the proponents have yet to contradict
it: "There seems to be no corroboratory depictions of any specific
mirror from the fifteenth century that could have been used in the
creation of the Arnolfini portrait, Lotto's 'Husband and wife,'
or indeed any of the paintings for which Hockney and Falco and I
computed an effective mirror focal length. In every case, particularly
the mirror proposed by Mr. Hockney, the focal lengths are much too
 Seeing the Light: Optics in
Nature, photography, color, vision and holography by David Falk,
Dieter Brill and David Stork, Section 6.2D (2000, 14th printing)
 "Mirror Images," by
Jennifer Lee Carrell, Smithsonian, pp. 76-82 (February, 2002).
method of Hockney and Falco is ill-suited to capturing subtleties
of surface -- color, chiaroscuro, sfumato, and so on. Because
the light is so dim in these projections, colors are harder
to distinguish. For instance, the red paint the artist wishes
to use appears quite different when illuminated by the red projected
light -- the hue, saturation and lightness are changed. Moreover,
colors appear different when dim, due to visual processes such
as the Purkinje shift. All these reasons show why it extremely
difficult to get the colors right by the Hockney/Falco method.
four statements are either incorrect (first and second) or irrelevant
(third and fourth). Getting the colors "right" is
a loose concept in the context of analyzing the efforts of a
painter who worked 600 years ago, as opposed to the context
of someone whose job might be ensuring visually undetectable
chromaticity variations between batches of color copier toner.
For example, we have no way of knowing whether or not Mrs. Arnolfini's
dress was even green (perhaps it was magenta), nor whether van
Eyck might have intentionally selected a more or less vibrant
shade of color for aesthetic reasons. Also, far from being "ill-suited
to capturing the subtleties of surface" as Stork incorrectly
asserts, oil paint in conjunction with optical projection is
precisely the combination of medium and technique that is almost
ideally suited for these subtleties.
Falco and Graves are mistaken on
this point. Suppose you are looking at an image projected onto your
white canvas for example the image of a red apple. What color paint
should you apply to the canvas to make the painting appear correct
to you under such circumstances? Artists especially: take a moment
to think about it. Should you apply red paint? No. WHITE! You should
paint the apple area, and indeed the whole canvas, white -- like
a movie screen. That way the projected image appears to you in its
Now suppose you're looking at the
dark projection and you want to paint the apple area so that it
will appear red under normal neutral illumination, that is, when
the painting is hung on the patron's wall. What color should you
paint it now? This is actually a very difficult problem and artists
would have to work very hard to get it right . The color your
paint appears changes significantly under the colored light. If
you put down red, it appears too saturated under the projection.
The cognitive and perceptual force, so to speak, is for the artist
to apply unsaturated colors, that is, more like white. But then
the painting will appear washed out and unsaturated under neutral
illumination on the patron's wall. It goes without saying that we
have seen no corroboratory evidence from the historical record --
manuals, descriptions, guides for artists -- showing that anyone
in the 15th-century had to confront this thorny problem. Didn't
any artist get the colors wrong in this challenging task? All the
'optical' artists magically figured out this extremely complicated
problem with no mistakes?
Then there are several relevant phenomena
of which I suspect none of the proponents is aware -- one's I've
studied for years. One of them is the Purkinje shift, in which colors
appear to change in hue and relative brightness when they are dim,
as in a projection in the Hockney/Falco theory. There's not a shred
of evidence Hockney, Falco or Graves are aware of these problems
-- again, a classic case of "they don't even know what they
don't even know." As someone who has worked on color for a
quarter century, starting with my thesis on color vision at MIT
under Edwin Land, founder of the Polaroid Corporation and inventor
of the Polaroid Land camera, I view Hockney/Falco/Graves understanding
of the relevant science of color incredibly naive, at the very best.
Getting the color right is absolutely
essential to the art of the Renaissance. While Falco and Graves
may point to the fact that we don't really know the color of Mrs.
Arnolfini's dress, we do know her skin color. Do they think she
was purple? That Genevre de' Benci was really a black Ethiopian?
That the peach in Chardin's painting is green and the cabbage in
Cotán's still life blue? I displayed Campin's "A Man"
favored by Mr. Hockney as my example because it is essential that
his skin color appear correct, not because his red turban might
have been instead ochre. Getting the color right is essential and
despite Falco and Graves's unsupported assertion, getting this color
correct is never aided by the projection method. In fact, if you
paint under the projection, you'll get the colors wrong -- or at
the very least, have to work extremely hard to get the colors right.
Perhaps color was just part of the
Mr. Hockney's difficulties when he is reported to have said at the
New York symposium: "I tried painting under an optical projection,
but it was too hard. I gave up within ten minutes. I'm sure that
if any Renaissance artists tried they would give up within ten minutes,
too." (Christopher Tyler, James Elkins and Amy Ione, pers.
And yes, it is human faces that most
expose the problems in copier toners -- a slight error and faces
look terrible. If you don't get the faces right in your color copier,
no one will buy it; if you don't get the colors of the faces correct
in your Renaissance portraits -- if you paint over the projected
image using the Hockney/Falco method -- no one will commission you
to do another portrait.
 Seeing the Light: Optics in
nature, photography, color, vision and holography by David Falk,
Dieter Brill and David Stork, Sections 9.6-9 (2000, 14th printing)
Hockney and Falco
give us no corroboratory evidence from fifteenth-century Europe
that a concave mirror was ever used for producing an image (rather
than burning). Scholars and historians of science and technology
have uncovered numerous obscure devices and would never have
missed records for the concave mirror method, had such records
As we already
showed in the section on Focal Lengths, Stork is completely
wrong on the historical record. To repeat just one sentence
from our earlier section, Robert Gibbs writes about the concave
mirror shown in a 1352 painting: "The use of mirrors for
reading continued into the sixteenth century, and the second
(not the first) representation, of a variant type set in a leather
horn rather than on a fixed metal stand, appears on St. Jerome's
Again, it is Falco and Graves that
are just a bit off the mark. In the context of previous discussions,
or at least according to the relevant issue, by "producing
an image (rather than burning)" I clearly meant producing
a real inverted image such as that required by the Hockney/Falco
theory. This new evidence fails to provide such evidence. Concerning
this new evidence: the mirror is wrong, the image is wrong, the
use is wrong.
The errors in
Stork's objections that he lists in his "Case I" are
dealt with in the various sections of this response, so we won't
repeat them here.
Since I wrote at length about the
absence of "upward" brushstrokes that would be produced
according to the Hockney/Falco projection method, their silence
on this matter can be taken to mean they have no answer to it.
artists have remarkable abilities, and it seems plausible that
van Eyck, Leonardo, Caravaggio and other Renaissance painters
had the requisite talent to create their paintings without reliance
on optical devices.
of whether or not Renaissance artists had the skill to work
without optical devices is logically unrelated to the question
of whether or not they did indeed use them. The many independent
pieces of optical evidence we have assembled demonstrates that
some artists as early as c.1430 certainly did use lenses as
aids for helping produce some of the features in some of their
paintings. Whether or not those particular artists had the skills
to have precisely reproduced at the same level of detail the
same features in those particular works without having used
lenses does not bear one way or the other on the optical evidence
we have presented that they did indeed use lenses.
I disagree profoundly with the assertion
"optical evidence we have assembled demonstrates
that some artists as early as c.1430 certainly did use lenses."
At best, some might be consistent with the use, but in no case have
they proven it, surely not with the Lotto nor the Albergati nor
the Arnolfini portraits, which Christopher Tyler and I took to be
their "best shots." I'll return to this in the summary.
It is very difficult
or even impossible to make images of running animals, flying
birds, restless putti, dragons or angel wings by the methods
proposed by Hockney and Falco. The fact that extremely realistic
"optical" representations of these subjects appear
throughout Renaissance painting shows that many painters of
that time had the requisite drafting talent and visual memory
and did not need to employ optical devices.
Again, as discussed
in the previous section on Talent, whether or not many painters
"needed" to use optical devices is tangential and
misleading. The relevant question is whether our optical evidence
demonstrates that they did indeed use them. As we have shown
with a wide variety of evidence, they did. Also, neither Stork
nor Tyler seems to realize that a lens would have been used
by an artist as an aid when it helped them accomplish his or
her goals, but would not have been used when it did not. For
example, the complex shape and lighting of the chandelier in
van Eyck's "Arnolfini Marriage" would have been much
easier to produce with the aid of a lens, but the small dog
would have been eyeballed. That is, both projected and eyeballed
features are within a single painting.
I wrote a whole section on adoption
of technology which Falco and Graves claimed was not relevant, but
in fact it addressed and refuted the point they'd like to make here:
"Also, neither Stork nor Tyler seems
to realize that a lens would have been used by an artist as an aid
when it helped them accomplish his or her goals, but would not have
been used when it did not." It is by no means so simple.
Let me proceed by an example, literally
at hand. Let us assume for the sake of argument that all computers
support graphics and text processing, but that the Macintosh is
better for graphics and the IBM PC is better for text. You produce
colorful art newsletters, and thus must do both. It took you a few
months to learn, but now you're a happy Mac user and do both graphics
and, with occasional annoyances, text processing, producing your
newsletter week after week. Now a salesman comes to your door and
tells you that you could write your text better if you used a PC.
The "search and replace" and spell checker functions are
much better on a PC, he convinces you. All you have to do, he continues,
is buy a PC and switch back and forth between computers, as needed.
He doesn't say that you must buy an extremely rare and expensive
PC on the black market, no one is advertising to let you know where
to buy it, that it will take a while to learn how to use it, that
there are no manuals, that your keyboard will be upside-down, that
you must work under a dark tent, that your screen will be upside-down
and nearly black, that you can't work except when the sun is shining,
that the color of the text will come out wrong unless you make allowances
at every keystroke and that if the police find you with the PC they'll
put you in jail. "But some text functions would be better!"
Would you buy a PC?
Now let's take Lotto. There's no
question that Lotto and numerous Renaissance painters could paint
optically without recourse to optical devices; the challenge image
of "Angel of the Annunciation," Leonardo's "Last
Supper," logic, and Falco and Graves's silence on such images
shows that. Lotto could render convincing images of the face of
the angel and of course much more. Now some late afternoon Lotto
is painting two patrons in his studio -- a husband and his wife
-- and has painted their faces, just as he had for the angel. Mr.
Hockney, magically teleported to the early Renaissance, enters the
studio and tells Lorenzo that he could capture the carpet pattern
better if he uses a new "PC," or "projection contraption."
All Lotto has to do is find this extremely rare and probably nonexistent
wonderful contraption, learn how to use it without a manual, learn
to deal with images upside-down that are very dark, set up a dark
tent in his studio, wait until next morning when the sun is shining
and hope the sky isn't overcast, struggle at each brush stroke to
get the colors right, and make sure that the Catholic Church doesn't
find out or they'll burn him at the stake. "But the carpet
pattern would appear better!" Would Lotto use Mr. Hockney's
Obviously, when Falco and Graves
write: "That is, both projected and eyeballed
features are within a single painting" they haven't
thought about points 4 and 5 on my technology section, perhaps because
they feel they are "irrelevant." The simple fact is that
switching back and forth "within a single
painting" would be extremely difficult, costly, awkward
and annoying, and would probably outweigh any putative benefit hypothesized
for the projections.
has never been to Hockney's studio, he makes the claim: Hockney
traces the image, rather than paints directly.
statement is irrelevant, it is also incorrect. As one of us
(CF) can attest, he does both, since CF personally witnessed
his own portrait being painted directly from Hockney's pallette
using an image projected by a lens.
I and many others would be very interested
in seeing this. The statement "Although
Stork has never been to Hockney's studio" seems to express
dismay in this regard. If Mr. Graves and Mr. Hockney would open
their studio to me, I'd be happy to come, and would bring a camera,
light meter and measuring tape. Regardless, it is hard indeed to
reconcile the above claim by Falco and Graves with Hockney's statement
at the New York symposium: "I tried painting under an optical
projection, but it was too hard. I gave up within ten minutes. I'm
sure that if any Renaissance artist tried they would give up within
ten minutes, too." (reported by Christopher Tyler, James Elkins
and Amy Ione, pers. comm., 2002).
The entire discussion
about the Hockney/Falco theory would be advanced significantly
if someone were to do what is accepted in other debates of which
I am familiar, particularly those relating to simple inexpensive
technology: attempt to re-enact as faithfully as possible the
methods that are claimed by the theory. This means, for instance
using a mirror
such as Hockney and Falco infer for Lotto's "Husband and
wife" (f = 54 cm, diameter = 2.4 cm)
(not tracing outlines), since as far as I know infra-red photography
has revealed no pencil or other sharp outlines in the underdrawings
of the vast majority of "optical" paintings in fifteenth-century
use a canvas
the size of the original, such as the Lotto (96 x 116 cm) or
Caravaggio's "Supper at Emmaus" (141 x 196 cm), the
latter portraying figures at nearly life size
Hockney has done
all of these things, and much more, in the course of the discovery
process over the past several years. This "experimentalist's"
approach to art history was instrumental in helping deduce the
techniques Renaissance artists used in painting with projected
images, and in testing the plausibility of various ideas from
the point of view of a working artist.
use no electricity
or modern illumination whatsoever, and be as faithful to constraints
upon illumination that we know, for a Caravaggio that means
working in a dark room such as a cellar
Once again, the
source of illumination was sunlight, not candles. As we noted
earlier, Stork oddly (albeit, inconsistently) assumes the contents
of paintings are literal representations of reality. This has
resulted in his incorrect inference here that for Caravaggio
to have painted a scene of a dark cellar meant he must have
painted it in a dark cellar.
Again, it is impossible to argue
against proponents of a theory who write that Caravaggio "...worked
in dark rooms -- cellars -- very common in those days... He used
artificial lighting" on the one hand and "direct
sunlight is the likely source of illumination" on the
does not contain anything relevant.
It does. And if Hockney, Falco or
Graves had the slightest experience in this matter, they'd know
it. As I wrote before, and in light of my discussion of Mr. Hockney's
"PC," even if somebody someday finds some long-focal length
concave mirrors from the Renaissance, it hardly means any artist
would have one or would even want to use it. The proponents naively
think that if a tool gave a "benefit" to artists then
of course they would in fact use it, but this is often far from
and Falco state their theory applies to such a broad range of
paintings over centuries, it should be able to account for difficult
cases ("challenge images") chosen by others, not just
those picked by the proponents themselves (e.g., "Rosetta
The above statement
shows a fundamental misunderstanding of the problem. Even though
no reasonable person would doubt modern photographs are produced
using lenses, few photographs actually contain sufficient information
to allow calculating anything about the lenses that were used.
For example, [Fig. 4] could have been taken with a 20 mm wide-angle
lens at a relatively close distance, or with a 500 mm telephoto
lens from a distance 25 times as far away. This image, like
the majority of images (photographs as well as paintings), does
not happen to contain the information we need to determine the
details of the lens used, even though there is no question about
the basic point that a lens of some kind definitely was used
to project this image onto the film.
Falco and Graves make a convenient
misquoting of me. The actual text from my piece is "Because
of the breadths of its claims, the theory then must be able to explain
-- or at the very minimum, be consistent with -- other 'optical'
paintings in the period." Contrary to their assertion here,
I'm not saying that they have to deduce properties of the mirror
used, just that they have to be consistent with the use of a mirror
and inconsistent with other plausible explanations. It is clear
now to all that these challenge paintings are not consistent with
the use of a mirror. That was my only point, and they surely haven't
Analyzing a particular
photo collage might be instructive if anyone else shares Stork's
confusion on this key point. Rather than attempting to secure
permission to reproduce a copyrighted work, instead we refer
people to their libraries for the April 2001 issue of 'Popular
Photography' magazine for a particular example. About one of
Mitchell Funk's photographs the article says '"I shoot
a lot of different images in similar light so they can be combined
without actually looking like a collage,' says Funk... 'I try
to keep...perspective believable when multiple shots are used.'
He added two elements: the sky and the man on the left in the
brown trench coat... Funk used the Photoshop draw tool to create
the man's shadow."
Funk is a skilled photographer who has been creating such collages
for at least 25 years, and even though he states he deliberately
attempted to keep perspective in this photograph believable,
he drew the shadow of the man in the brown coat at the wrong
angle. This created a second vanishing point, the presence of
which betrays the fact this photograph is a collage. However,
had Mr. Funk instead drawn the shadow to have the same vanishing
point as those from the lamp post and the other pedestrians,
there would have been no way to know it was a collage. The point
being, even for photographs, about which there is no question
whatever that they were produced using lenses, it is impossible
in most cases to deduce anything about the lenses used. Only
when the photographer (painter) has failed to adequately conceal
the artifacts of the use of a lens can we hope to find the evidence
within a given image.
If Lotto had
instead placed a large platter on the table of "Husband
and Wife" as he did 20 years later when he used a similar
composition for "Giovanni della Volta[Fig. 5]," and
had he taken just a bit more care with the border of the tablecloth
at the right, he very easily could have made it impossible for
us to prove he used a lens. Fortunately for us, Lotto failed
to conceal the distinctive optical artifacts that allowed us
to make our calculations in Reference 4, providing invaluable
scientific evidence in a quest that led us to a variety of examples
of the use of optics in paintings as early as c.1430.
The issue is not whether we can deduce
properties (e.g., focal length) of a lens in a "platter"
Lotto, but whether we can say that a lens was used at all. If there
is no evidence, then we cannot claim it. Simple. And given the challenge
images that prove that no lens was used, there's no reason to assume
that a lens was used for the "platter" Lotto, especially
when the evidence for mirror use is so contradictory or non-existent,
as in "Husband and wife."
Falco and Graves make several errors
in logic here. The first is their assertion "no
question whatever that they were produced using lenses."
But this is precisely the matter at hand in the case of Lotto; there
is every reason to question that Lotto used a lens. Indeed there
is no persuasive evidence that he did, and surely no disproof of
the traditional explanation that he didn't use a lens.
Here's a parallel story. Suppose
Mr. Falco analyzes a still from Steven Spielberg's film "Little
Women" and finds there's enough information to properly deduce
the focal length, aperture or other properties of the camera lens
used. Now he turns to a still from a scene in a different film by
Mr. Spielberg and finds there isn't enough evidence to deduce such
properties of the lens. "Well, since there is no question Spielberg
was using a lens," we imagine Falco stating, "the inability
to deduce its properties doesn't disprove the use of a lens."
Too bad for Mr. Falco, though. The later Spielberg film is "Jurassic
Park," and the still came from a scene which was created entirely
by computer -- no lenses (or even objects) whatsoever. Given we
know for certain Spielberg, John Lasseter, and others can make films
that contain images made without any recourse to standard cameras
and lenses, as shown by "Toy Story II," and so on, the
flaws in Mr. Falco's are clearly exposed. The whole discussion has
been over whether Renaissance painters used optics, and Falco's
flawed logic cannot salvage the inability to show optics was used
in the hypothetical evidence-poor Lotto "platter" painting.
But it is even worse than that for
the optical theory because Hockney, Falco and Graves have given
us no evidence that a lens must have been used in any Renaissance
painting, though they'd desperately like others to believe they
have. By analogy, they haven't shown that Spielberg used lenses
at all in "Little Women." The burden is entirely upon
the theory's proponents to show that the traditional methods are
insufficient to explain properties of any painting, and that the
optical projection method must have been used. Despite being gven
numerous opportunities, they have failed to do this in even a single
this site Christopher Tyler and David Stork stated various objections
to our evidence that certain Renaissance painters as early as
c.1430 used lenses as aids for some of the features in some
of their works. However, as we have shown, all of Tyler's and
Stork's objections arise from their errors in logic, lack of
historical knowledge, or misunderstanding of perspective, resulting
in none of them having any relevance whatever for the evidence
reported in either Reference 1 or Reference 4. To summarize:
lists six objections, only two of which address in any way our
optical evidence. However, as we have shown, these two objections
are based on Tyler's simple misunderstanding of optical perspective,
which in turn resulted in him arriving at incorrect conclusions.
His other four points have no bearing on either the scientific
or the visual evidence.
arguments reduce to: 1) there is no historical documentation
of the existence of appropriate mirrors and lenses during the
early Renaissance; 2) artists had sufficient talent that they
wouldn't have needed to use lenses anyway; and 3) it would have
required an impossible number of candles to provide sufficient
illumination to use such lenses. We have shown above that 1)
documentation certainly does exist that demonstrates appropriate
mirrors and lenses were being produced and used as imaging devices
as early as the 13th century; 2) the question of whether or
not artists had the talent to paint without the aid of lenses
is a logical red herring, unrelated to evaluating the evidence
we have presented that, irrespective of their skill level, certain
of them indeed did use such lenses; and 3), as we clearly stated
in New York, they didn't use candles, they used sunlight.
For anyone who
has taken the time to read this far, it is perhaps worthwhile
to briefly summarize "lenses"-refractive lenses or
concave mirrors-to aid them in creating portions of certain
of their paintings. Within those paintings we have studied that
show evidence of the use of lenses, every optical artifact we
have identified is consistent with having resulted from the
use of lenses to project portions of the images. Where sufficient
details exist to allow us to extract quantitative information
(e.g., of focal length or lens diameter), the values we determined
are not only reasonable, they have allowed us to quantitatively
reproduce the observed effects photographically. Further, we
have found no features that are inconsistent with the use of
optics (e.g., something that implied, say, an unrealistically
short or long value for a focal length).
They state: "Within
those paintings we have studied that show evidence of the use of
lenses, every optical artifact we have identified is consistent
with having resulted from the use of lenses to project portions
of the images." Here's a counter-example: the local
convergence of parallel lines in Lotto's "Husband and wife."
Here's another: They claim that van Eyck used the convex mirror
depicted in the Arnolfini portrait to paint the image itself, but
this is impossible. Most importantly, every feature in every image
Hockney and Falco put forth is consistent with non-optical explanations.
Again, there are innumerable examples that are inconsistent with
the optical hypothesis -- murals, ceilings, self-portraits, objects
in motion, etc. Moreover the long-focal length concave mirrors implied
by numerous paintings are unknown from that time.
A lens isn't
merely the simplest explanation for the discoveries reported
in Reference 1, it is the explanation that accounts quantitatively
and qualitatively for everything that we have discovered. Rather
than invoking separate ad hoc reasons for each distinct optical
artifact we have identified, or using the opaque shroud of "artistic
genius" as a substitute for comprehension of any of this,
we emphasize again that all the optical evidence we have discovered
is explained by the properties of concave mirrors and lenses.
Wide new areas of inquiry are now open to pursue the implications
of these discoveries.
Contrary to the Falco and Graves
assertion, it is the Hockney/Falco explanation that is ad hoc and
inconsistent. For instance, Hockney tells us that Cardinal Albergati
has small pupils because he's under bright illumination needed for
the mirror method -- so then why don't Arnolfini, his wife, Campin's
"Man," and innumerable others claimed to be made by the
method also have small pupils? And why do some subjects in 'non-optical'
paintings, such as Berhhard Strigel's 'Portrait of a man,' also
have small pupils? We're told that the mirror projection method
leads to "blur" in Lotto's "Husband and wife"
-- so then why don't we see the same in Caravaggio's "Supper
at Emmaus," Holbein's "The Ambassadors," and Arnolfini,
also claimed to be made by the method? Each of these explanations
is arbitrary and ad hoc. Finally, never I have employed some "opaque
shroud of 'artistic genius'" -- I don't need to -- and
Falco and Graves are attacking a strawman of their own making.
After Thought Summary
Hockney, Falco and Graves have yet
to provide a single painting from the early Renaissance that requires
the use of optical projections. Their favored Albergati portrait
can easily be explained by non-optical methods, in fact much easier
than with optics. The carpet in "Husband and wife" could
not have been done with optics as they claim, as the local convergence
lines are not consistent, though they would have to be in an optical
projection. Moreover, the very slight blur (which curiously only
occurs in this painting) can be explained by numerous non-optical
ways. They have provided corroboratory evidence for neither the
optical elements (long-focal length concave mirrors) employed by
their theory, nor the projection method itself, even though there
is every reason such evidence would otherwise be available, the
Inquisition and conspiracy theories notwithstanding.
The optical theory is incoherent,
arbitrary and ad hoc: Bright illumination leads a sitter (Albergati)
to have small pupils -- except when it doesn't (all others). Blur
in a painting (Lotto), "proves" a concave mirror was used
-- but when there is no blur, well, a concave mirror was used there
too (Caravaggio). There is an enormous number of Renaissance paintings
that we know for certain were not created using optics (challenge
images and related) and the burden is upon the proponents to disprove
the traditional explanations (and account for ancillary supportive
and contextual facts). The proponents give no persuasive explanation
for the lack of inverted brushstrokes or why historians are so wrong
(e.g., on Caravaggio's working methods). Contrary to the proponents'
unsupported assertions, getting the color right is never aided by
the projection method, and in other cases is impeded significantly,
as explained above. This difficulty could explain part of Mr. Hockney's
frustration with his technique, reported from the New York symposium:
"I tried painting under an optical projection, but it was too
hard. I gave up within ten minutes. I'm sure that if any Renaissance
artist tried they would give up within ten minutes, too." If
Renaissance painters didn't paint under projection, then there should
be trace lines, revealed on at least some paintings of the time;
the proponents have yet to provide them for any painters, let alone
their favorites, such as van Eyck and Lotto. The proponents seem
incapable or unwilling or both to give alternate explanations, and
many objections; a look through Secret Knowledge, the OPN
paper and elsewhere shows no identification and surely no resolution
on many of these alternative explanations or problems, such as grids
and color. The proponents espouse in print searing contradictions
on central matters on their favorite examples (e.g., illumination
The breakthrough in these discussions
-- and what should really let us all close the books and go home
now -- is Falco and Graves's argument against pantographs for the
Albergati portrait, that is, the commonsense statement that the
simple device couldn't have been used since hadn't been invented
yet. But neither had the far more complicated long-focal length
concave mirror projection system, so mutatis mutandis, all their
optical examples are similarly disposed of. Lucky for me, I have
a preferred alternative explanation for the Albergati; unlucky for
them, they have no alternate explanation for any of theirs.
Falco states at every opportunity
that proof of their theory is a done deal, as if saying it enough
times to himself, Mr. Hockney, and a supposedly uncritical audience
will make it so: "Lorenzo Lotto used
a lens to make this painting in 1556; of this there simply is no
doubt" (SK), "It's
science; I proved they used optics" (NY Symposium, twice),
"some artists as early as c.1430 certainly
did use lenses" (above), "This
isn't a story... It's not your version versus my version. This is
fact. This is science." (Smithsonian), and on and on.
He must think Chris Tyler, I (PhD physics), and other skeptics are
too thick to worry about... In fact he effectively says as much:
"At this point there's enough evidence to convince any jury
of physicists to convict Lorenzo Lotto of use of an unregistered
camera obscura (a jury of art historians is another matter, of course)"
(SK) and "Anyone arguing...
that Memling didn't use a lens would be a person too thick to worry
about" (SK, also quoted in NY Times review of
SK). Finally my favorite, broadcast to over a million readers:
"You could convict OJ with this evidence"
Gentle reader: Flip back through
the discussions and see if you don't think there should be at least
a little doubt concerning the optical hypothesis. Consider a jury
of twelve, made up of artists, art historians, optical scientists
and general art lovers, say. Do you agree with Falco that all of
them -- unanimously -- would vote to "convict
OJ" in the optical case presented by Messrs Hockney,
Falco and Graves?
Finally, I have one simple request to
Hockney, Falco and Graves: Please stop calling a concave mirror a
"lens" (or even "mirror-lens"), as in the book,
OPN paper and elsewhere. It is not a 'lens,' and this abuse of standard
terminology only confuses things, particularly when the matter of
left-right reversals, chromatic aberration, flare, etc., arise. As
the Encyclopaedia Britannica Volume 15 (1964) states on page
591: 'Calling an astronomical [concave] mirror a lens is also a common
error.'. Likewise, I have no idea whether you call a convex mirror
a "lens" or "mirror lens" as well.
Earlier, both Christopher Tyler and I outlined numerous errors
and severe problems in the Hockney/Falco theory -- the glaring omission
of any corroboratory evidence that long-focal length mirrors existed
in the fifteenth century, or that they were used to project real inverted
images, or that anyone traced them, and on and on. I made very specific
quantitative and scholarly rebuttals to their claims on their primary
evidence -- I showed that the convex mirror in the Arnolfini portrait
could not have been used in the painting's creation as often claimed
by Hockney and Falco. Tyler showed that the Hockney/Falco explanation
of Lotto's "Husband and wife" led to implausible patterns
on the carpet. I exposed searing contradictions in the writings of
the theory's proponents (Caravaggio used artificial lighting; no he
worked by bright sunlight). I did specific re-enactment/experiments,
such as the grid construction of the Albergati portrait, showing alternate
explanations were not merely possible, but in fact more probable and
explained all the data much better.
While Tyler and I become more and more convinced of the profound technical
difficulties with the Hockney/Falco theory with every analysis, correspondence
with acknowledged scholars, careful reading of the historical record
and of the writings of Hockney and Falco themselves, I think even
the most ardent independent supporters of Mr. Hockney would have to
admit that there is at least some doubt about the theory. At minimum,
the fact that the first two scientists to analyze the theory, independently
chosen to attend the NY symposium, both reject it for complementary
sets of technical reasons should give anyone pause.
Nevertheless, Falco makes the following claims in highly visible
public venues that proof of the theory is a done deal:
- "Lorenzo Lotto used a lens to
make this painting in 1556; of this there simply is no doubt."
- "It's science; I proved they used optics"
- "some artists as early as c.1430 certainly did use lenses"
- "This isn't a story... It's not your version versus my
version. This is fact. This is science."
- "At this point there's enough evidence to convince any
jury of physicists to convict Lorenzo Lotto of use of an unregistered
camera obscura (a jury of art historians is another matter, of
- "Anyone arguing... that Memling didn't use a lens would
be a person too thick to worry"
- "You could convict OJ with this evidence."
I have never in my professional life seen such irresponsible statements
made in public forums by a reputable scientist, all without a single
peer-reviewed paper to back it up. Compared to Falco's charge I'm
making ad hominem arguments, I feel the above statements are immensely
worse, not just because they are incorrect, not just because they
are relentless, not just because they haven't a single peer-reviewed
article to back them up, but because they abuse non-experts' trust
in science and scientists.
Regardless: are my statements so out of line? Falco finds statements
such as the following so objectionable, that I'm making ad hominem
"... colors appear to change in
hue and relative brightness when they are dim, as in a projection
in the Hockney/Falco theory. There's not a shred of evidence Hockney,
Falco or Graves are aware of these problems -- again, a classic
case of 'they don't even know what they don't even know.'"
Before I wrote that passage, in good scholarly protocol I checked
every possible source: Secret Knowledge, the OPN paper, articles
in the popular press, a list of Falco's publications (which center
on condensed matter physics such as depositing atoms on computer chips);
I even tried to check on which courses Falco taught. Nowhere did I
see any evidence that the proponents knew the science of perceptual
psychology relevant to their theory. The word "color" doesn't
even appear in the index to Mr. Hockney's book! There is no reason
Mr. Falco's undeniable and extensive expertise in solid-state physics
concerning layers of atoms on computer chips automatically transfers
to the fields of human psychology and the neuroscience of color perception.
I indeed stand by my statement above. Falco could have been refuted
it very simply if he had any evidence. I'm sorry if Mr. Falco feels
this statement is ad hominem; I do not believe it is. I urge all readers
to read my the original text in context and see if it does not aim
-- as I intended -- to point out that there is a whole range of phenenomena
relevant to analyzing the theory that the proponents not only overlooked
but indeed are unaware of.
comparison, to see if I am so out of line as Falco claims consider
the two most recent published documents to cross my desk in this
matter, both reviews of Secret Knowledge. In the New York
Review of Books, Ingrid D. Rowland conveys the point I was trying
to make in the passage Mr. Falco found so objectionable and, one
must admit, in a personal and unflattering way:
"In the debate engendered by Secret Knowledge, David
Hockney spoke of his own deafness, and it is hard to resist taking
this condition metaphorically; it brings on inner visions at the
price of stopping convesation. He and Charles Falco have become
true believers in a world that is to a great extent of their own
second appears in Blake Gopnik's review in the Washington Post:
"...Hockney has at last set out his idea in detail in this
lavish coffee-table book, and it's left me staggered: It's hard
to imagine how you could fit more errors of fact, technical ignorance,
philosophical incoherence and logical inconsistency between two
covers. To come to grips with all of Hockney's missteps would take
many more words than he has used to set them out." and "The
book is a mess, in fact and in thinking." and "[Hockney's]
whole argument really derives from buying into his own hype."
and "Our culture doles out attention, even authority, based
on celebrity, rather than on evidence of talent, brains or knowledge."
reader: please re-read my After Thought in its immediate context
and those of other writers on the topic, and the list of quotations
from Falco, and judge for yourself whether it is Falco or I who
has "chosen to leave the arena of serious
scholarly debate" in the phrase given by Falco.
Tyler and I are submitting articles to scholarly forums, and have
just begun giving public presentations refuting the claims of Hockney
and Falco; we will continue to do so. Of course we are at a tremendous
disadvantage -- caught off guard, late to the gate, and without
the media draw guaranteed by Mr. Hockney. For instance, the same
day (March 1) I gave a roundtable presentation to roughly 20 scholars
in the Stanford University Art History Department (including a Caravaggio
expert), Mr. Hockney gave a big public lecture in New York to hundreds,
no doubt with extensive popular media coverage.
very glad indeed that Falco will begin to present evidence to scholarly
forums, rather than unrefereed or public media that has bouyed interest
in the theory up to now -- such as Optics and Photonics News, Smithsonian
magazine, High Life magazine, the BBC film which contained no alternate
views or countervening evidence... I am confident that with the
careful and appropriately skeptical analysis by those with expertise
in optics and art (and perception) the correct negative verdict
will be rendered, just as to my knowledge not a single scholarly
review of Secret Knowledge has been positive.
even when -- as I predict -- the theory will not survive such scrutiny,
it will be too late. The public will have lost interest, hundreds
of thousands of copies of Secret Knowledge will have been
sold, millions will have seen the BBC documentary, and Hockney's
profoundly flawed theory will have seeped into the cultural fabric.
Incidentally, I submitted a letter to Smithsonian magazine pointing
out what I felt were gross errors in their February article and
interview with Hockney and Falco -- an article most noteworthy in
that its author apparently spoke with not a single person with an
alternative view! The resulting letter, as printed in the April
issue, was edited severely and changed to introduce errors, all
without my being given an opportunity to see the revisions. (For
instance, they inserted the error that Caravaggio worked in a "cave,"
whereas I had written "dark cellar," as Mr. Hockney and
scholars attest.) For the record, the original letter I submitted
As one of the two scientists at the December Art and Optics symposium
invited to analyze the intriguing Hockney theory (both ultimately
rejecting it), I read "Mirror Images" [February, 2002]
with great interest. What your article did not point out is that
murals, ceilings, self-portraits, moving objects and non-existent
objects (e.g., dragons) cannot be recorded by the Hockney/Falco
method; that because Caravaggio worked in dark cellars by artificial
light (as Mr. Hockney and art historians attest) he must have used
over 1000 candles at a time; and that virtually all brushstrokes
visible in paintings or hidden beneath (revealed by modern infra-red
photography) are "downward" contradicting the theory that
paintings were at least partially executed upside-down. While the
proponents claim the use of concave mirrors was "baby optics"
and "[I]f it's that simple, artists will use it," in fact
it wasn't baby optics in 1430; the manufacture, test, and use of
long-focal length concave mirrors would have been the most complicated
optical engineering achievement on the planet ˜ their "Hubble
Telescope." Don't forget that perspective constructions, familiar
to every schoolchild with a ruler and pencil, consumed the greatest
mathematical and architectural minds of the fifteenth-century and
led to numerous scholarly treatises. Moreover, despite historical
records of all manner of obscure optical and drawing devices ˜ from
anamorphic mirrors and the bacolo of Euclid to zoetropes and zograscopes
˜ there is no corroboratory evidence over centuries for the required
mirrors in their hypothesized projection use ˜ not even a passing
But the strongest arguments against the theory come from detailed
and careful analysis of the paintings themselves. A brief example:
You quoted Mr. Hockney's claim that the famous convex mirror in
van Eyck's Arnolfini portrait could be turned around and used
for the projection method. However the convex mirror has strong
focusing power (is bulged like the stomach of a woman 8 months
pregnant) while the mirror required for projection has weak focusing
power (bulged like a woman just 2 weeks pregnant) ˜ the depicted
mirror could not have been used as claimed.
considerations, and others like them, both deepen our understanding
of Renaissance art and argue against the Hockney/Falco theory.
David G. Stork, PhD
Consulting Associate Professor
Departments of Electrical Engineering
and Computer Science