|Errors in Stereo History & The Chimenti Hoax|
|by Abram Klooswyk, compiled with kind permission from postings to photo-3d|
Errors in Stereo History
Some people seem to ignore the fact the that there exists a wealth of scientific literature on the opinions on vision and binocular vision in the past.
Two main errors in discussions frequently occur:
1) The fact that in past centuries was known that both eyes see things a little differently is accepted as evidence for knowledge of stereoscopy or stereoscopic imaging.
2) In any age stereo images (drawings) could have been made, so something might be found in an African cave (e.g.).
To 1.: This has been written by Brewster in 1856. It has been shown over and over to be erroneous. Euclid in his treatise on optics only said that more of the surface of a sphere is seen with two eyes, Leonardo knew that a painting can never show the "relievo" of reality, and he showed that an object covers different parts of the background for either eye, but he didn't go any further. All pre-Wheatstonian so called stereo drawings or paintings have been shown to be accidental or otherwise in error. Brewster's opinion are still found back in many books and on many web sites.
To 2.: This is similar to the opinion that a monkey with a typewriter could write Shakespeare plays, if given time. It completely ignores the fact that the development of imaging through the centuries is in pace with the general cultural development. Cultures which didn't have central perspective are far from getting to stereo imaging.
Perspective in painting was used long before the Renaissance, some Pompei wall paintings show use of perspective. However central linear perspective was not used before the end of the 15th century. Why not? Studying Euclid's geometry would be enough for making drawings with central perspective. The reason is that the world image was not developed far enough. The middle ages must end before central perspective could emerge.
Many artists and scholars up to the 19th century were fully aware of perspective laws and they did many experiments on binocular vision. This didn't lead to the discovery of stereoscopic imaging or the causes of stereopsis. Why not? The world image was not developed far enough.
I have written earlier on similar subjects several years ago. (Summary see < http://www.pauck.de/archive/mailinglist/tech-3d/mhonarc/msg01454.html>). Since then I have found more literature, especially writings by Nicholas Wade.
- Wade, Nicholas J. "A natural history of vision". Cambridge, Mass. ; London : MIT Press, 1998. (466 pages).
In this book the history of scientific writings on vision are discussed, with hundreds of quotes from Aristotle to the mid 19th century. Binocular vision is an important subject in it. The book is indispensable if you are interested in the subject.
- Wade, Nicholas: Guest editorial - Charles Wheatstone (1802 - 1875).
Perception 2002 vol 31 p 265-272.
Professor Nick Wade had previously discussed why visual scientists for centuries failed to discover stereopsis, in the paper:
- Wade N. J. "On the late invention of the stereoscope".
Perception 1987 vol 16 p 785-818.
A very interesting book on the visual culture of the 19th century, and especially how this led to the invention of stereo imaging and the stereoscope is:
- Crary, Jonathan. "Techniques of the observer: on vision and modernity in the nineteenth century".
Cambridge, Mass. ; London : MIT Press, 1990. (171 pages).
In conclusion, errors on stereo history are abundant, they only seem to demonstrate the general ignorance on the subject and the fact that some have strong opinions without the slightest inclination to do some research on the subjects on which they have those opinions.
The Chimenti Hoax
I can hardly Believe My Eyes to see the Chimenti drawings again advertised as stereo drawing. This is an old hoax on which the debate started about 1860 and practically ended about 1867, but of course erroneous repeats appeared over and over - until today.
Today anyone how has opinions about Chimenti should first read the full story, which last year has been spelled out in:
- Nicholas J Wade, "The Chimenti controversy".
Perception, 2003, volume 32, pages 185-200,
A PDF version of it is on-line available in many (university) libraries, it is 1440 kB, but copyrighted, so I cannot quote or post it entirely.
The abstract says: "Jacopo Chimenti (1551-1640), an artist from Empoli, made two sketches of a young man holding a compass and a plumb line. When these were seen, mounted next to one another, by Alexander Crum Brown in 1859, he combined them by overconvergence and described the stereoscopic depth he saw. Brown's informal observation was conveyed to David Brewster, who suggested that the drawings were produced for a stereoscope, possibly made by Giovanni Battista della Porta. There followed a bitter debate about the supposed stereoscopic effects that could be seen when the pictures combined. Brewster's claims were finally dispelled when precise measurements were made of the drawings: some parts were stereoscopic and others were pseudoscopic. Brewster's attempts to wrest the invention of the stereoscope from Wheatstone were unsuccessful."
I quote some essentials from the paper.
David Brewster, then President of the Photographic Society of Scotland, had a letter by Crum Brown printed and he added: "This account of the two drawings is so distinct and evinces such knowledge of the subject, that we cannot for a moment doubt that they are binocular drawings intended by the artist to be united into relief either by the eye or by an instrument. This conclusion is the more probable as the drawings must have been executed before 1640, the year in which Chimenti died at the age of eighty-six; and it is highly probable that they were executed soon after 1593, when Baptista Porta had published the Theory of the Stereoscope, and when Chimenti was in his fortieth year".
Note that Brewster at that time had not himself seen the drawings, or photos of them!
When copies arrived, in the meeting of the Photographic Society of Scotland all agreed that they were stereoscopic. Of course, Brewster had an enormous authory, he had invented the lenticular stereoscope and had proposed a stereo camera, and also had written "The Stereoscope" (etc), all before or in 1856. So who dared to contradict him in Scotland?
Brewster had claimed that the principles of binocular combination had been known for centuries.
"Brewster was conflating optics and observation, that is, the geometry of optical projection with its perceptual consequences. Dissimilar projections to each eye had long been known, but the visual consequences of this were first described and demonstrated by Wheatstone (1838)." (Wade)
"Printed communications were swift in the nineteenth century. Brewster's initial description of the Chimenti drawings was read to a meeting of the Photographic Society of Scotland (of which he was President) in March, 1860; reports of the lecture were printed in both British and Continental journals, and responses were quick to appear."
On the continent Brewster's authority was not so self evident. "At a meeting of the French Photographic Society, in July 1860, photographic copies were said to unite but not to provide any stereoscopic effect."
"Mr. Bingham, who has just returned from Lille, conceived the happy idea of reproducing the two designs in question to offer them to the Society." "For the present, then, we must be permitted to doubt that they were intended for the application Sir David attributes to them." (Lacan 1860).
Prof. Kuhlmann of Lille send photographs of Chimenti's drawings to Wheatstone, adding: "...it would seem that the two pictures were not stereoscopic." (1860).
William Benjamin Carpenter wrote in The Photographic Journal of 1862: "In the stereoscope there was a certain amount of relief, but not such relief as to lead him to the conviction that they were produced by anyone knowing the theory of binocular vision. The most important thing, to his mind, was the fact that the perpendicular lines did not coincide. The lateral lines ought of course to vary in proportion to the variation of angle at which they were taken; but the perpendicular lines ought to correspond. This was not the case: the distance between the epaulette and the tail of the doublet in one was greater than in the other; and, as a gentleman had pointed out to him since he came into the room, the distance from the foot to the knee was greater in one than in the other. In addition to these deviations, there was another material one: in one of the figures the head appeared looking down considerably more than the other; so that whilst the knee appeared in relief, the appearance of the head was confused. To get the head in relief, the pictures required turning a little. If the pictures were transposed, some parts were slightly stereoscopic, but the rest a mass of confusion. Again, the stool in one formed a horizontal line, whilst in the other it sloped to the back of the figure. He could not but think that Sir David Brewster had failed in exercising his usual discretion in supposing these pictures to be drawn on stereoscopic principles, or with a knowledge of the theory of binocular vision".
However, Brewster was not one to make concessions in a controversy.
Wade: The controversy spread across the Atlantic, and Edwin Emerson, a professor at Troy University and a keen photographer, entered into it wholeheartedly.
His first report appeared in The American Journal of Science and Arts. He noted (1862): "A remarkable instance of the uncertainty attending the perception or non-perception of stereoscopic relief, even in cases where we might suppose there could be no want of knowledge is shown by the controversy now going on in Europe over The Chimenti pictures. Sir David Brewster thinks he has in these pictures a specimen of real stereoscopic drawings produced about the middle of the 17th century (...). I have made careful examination of the photographs of these pictures, and the truth is that the trifling stereoscopic and pseudoscopic qualities about them are evidently accidental".
Wade: Emerson (...) measured the dimensions of the two drawings, and a colleague did so independently. The outcome was clear: "As Sir David Brewster requires particulars, we enumerate:- A stereoscopic left knee, a pseudoscopic dress hanging over it, a stereoscopic left arm, but a pseudoscopic back, a pseudoscopic stool, and a pseudoscopic left foot, and a right foot still more pseudoscopic relatively to the left foot and the stool; and so we might go over the whole picture and show a mélange of pseudoscopic and stereoscopic lines, producing precisely the commingled and uncertain effect which a drawing and an ordinary copy of it would produce if adjusted for the stereoscope. And yet these are the pictures that Dr. Crum Brown 'succeeded in uniting so as to produce an image in relief' and they united for him 'easily and completely!' These are the pictures which Sir David Brewster claims, gravely and persistently, a high 'degree of stereoscopic effect,' and on that account boldly proceeds to gibe the seventeenth century the high honour rightly belonging to one of the most beautiful discoveries of our own age!" (1864)
Wade: Whether Brewster saw the error of his ways we do not know, but he did not re-enter the fray. The controversy was at its height when Helmholtz was writing the third volume of his Handbuch der physiologischen Optik, which treated stereoscopic vision. He gave a sober description of the arguments, and provided another possible interpretation: "D. Brewster conjectured that the pictures may have been made by Chimenti to test Porta's theory, which was published in 1593. Since then photographic reproductions of these pictures have been made for sale. The two pictures of the man were certainly made from different positions, but I must admit that it seems to me very unlikely that Chimenti intended them for a stereoscopic experiment, because the stool, the dividers, and the plumb line, which could easily have been drawn correctly, are treated as unessentials and all drawn so irregularly and so differently that they cannot be combined. Had the artist desired to test a theory, it is more likely that he would have drawn the easy things correctly and the difficult parts, such as the man, more inaccurately. It seems more probable to me that the artist was not quite satisfied with the first figure and did it over again from another point of view, using the same sheet of paper quite by accident" (Helmholtz 1867).
Wade: The Chimenti controversy refuses to die. The mischief manufactured by Brewster has multiplied, and this misinformation has been mimicked many times on the internet. Not only are the Chimenti pictures described as the first stereoscopic pictures, but it is also stated that Porta (1593) produced binocular drawings, too! There are, indeed, many illustrations in Book 6 of Porta's De Refractione, which treats binocular vision.
They demonstrate clearly that he was lacking an understanding of image formation in the eye. Although Porta (1589) had previously made an equation between the eye and a camera obscura, he still believed that the seat of vision was the lens rather than the retina. The diagram that Brewster reproduced can be readily interpreted as a reflection of Roger Bacon's (c 1220-1292) analysis of binocular combination, and one that was commonplace in late medieval texts on optics.
Porta was advancing a suppression theory of binocular single vision (1593):
"Nature has given us two eyes, one on the right and the other on the left, so that if we are to see something on the right we use the right eye, and on the left the left eye. It follows that we always see with one eye, even if we think both are open and that we see with both. We may prove it by these arguments: To separate the two eyes, let us place a book before the right eye and read it; then if someone shows another book to the left eye, it is impossible to read it or even see the pages, unless for a short moment of time the power of seeing is taken from the right eye and borrowed by the left. We observe the same thing happening in other senses: if we hear someone talking with the right ear we cannot listen to another with the left ear; and if we wish to hear both we shall hear neither, or indeed if we hear something with the right we lose the same amount from the left. Similarly, if we write with one hand we cannot play a lyre with the other, nor count out coins. There is another argument. If someone places a staff in front of himself, and sets it against some obvious crack in the wall opposite, and notices the place, then when he shuts the left eye he will not see the staff to have moved from the crack opposite. The reason is that one sees with the right eye, just as one uses the right hand and foot, and someone using the left eye or hand or foot is considered a monster. But if the observer closes the right eye, the staff immediately shifts to the right side. There is a third argument - that nature made two eyes, one beside the other, so that one may defend a man from attackers from the right and the other from the left. This is more obvious in animals, for their eyes are separated by half a foot, as is seen in cattle, horses and lions. In birds one eye is opposite the other; consequently, if things must be seen both on the right and on the left, the power of seeing must be engaged very quickly for the mind to be able to accomplish its functions. For these reasons the two eyes cannot see the same thing at the same time".
So Porta. about whom Brewster said that he knew about stereoscopic theory and made a stereoscope, even denied that the eyes work together at all! And of course not the truth but the hoax is repeated till today. (A.K.)
Wade also quotes George Shadbolt, editor of the British Journal of Photography, who wrote in 1860: "It is very unfortunate that when an announcement of any supposed fact is once made, and subsequently proved to be erroneous, it is almost impossible to correct the false impression as thoroughly as is desirable, because there must always exist many persons who read the assertion but not the contradiction, while those who see the contradiction without the previous erroneous statement can play but a very unimportant part in its rectification".
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