Pro-optical

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[5] 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."[6] 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..."

Pro-optical

[5] Robert Gibbs, Tomaso da Modena (Cambridge University Press, 1989).

Pro-optical

[6] nb. In fact, when properly oriented, concave mirrors magnify the text without reversing it.

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 [2]. 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" [3].

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 short."

[2] 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)

[3] "Mirror Images," by Jennifer Lee Carrell, Smithsonian, pp. 76-82 (February, 2002).

Oil Paint

The projection 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.

Pro-optical

Stork's above 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 proper colors.

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 [3]. 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? Everyone 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. comm., 2002).

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.

[3] 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)

No Documentation

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 existed.

Pro-optical

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 shelf..."

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.

Arnolfini Portrait

Pro-optical

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.

Talent

Clearly, trained 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.

Pro-optical

The question 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.

Problems Tracing

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.

Pro-optical

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 "PC"?

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.

Demonstrations

Pro-optical

Although Stork has never been to Hockney's studio, he makes the claim:

Pro-optical

Although this 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).

• using a mirror such as Hockney and Falco infer for Lotto's "Husband and wife" (f = 54 cm, diameter = 2.4 cm)

• painting areas (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 Europe

• 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

Pro-optical

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

Pro-optical

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 other.

Technology

Pro-optical

This section does not contain anything relevant.

It does. And if Hockney, Falco or Graves had the slightest experience in this matter, they'd know it -- a classic case of "they don't even know what they don't even know." 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 the truth.

Future Discussions

Because Hockney 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 stone").

Pro-optical

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. 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 refuted it.

Pro-optical

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." Although Mr. 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.

Pro-optical

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. They have failed to do this.