Following a municipal council session, the township of Châlon-sur-Saône issued in 1877 a paper that had a significant influence on the historical attribution of the photography invention to Niépce alone, while leaving a sort of usurping role to Daguerre. In so doing, it was leaning on V. Fouque's works, a historian of local repute, some of Chevreul's incoherent ideas on the subject (1), and the unfounded allegations of Niépce's family.

Reading treatises dealing with the pioneering research of photography and its invention is indisputably a perplexing exercise to someone wishing to get proper information and to form an objective opinion on this intricate question. The same remark applies to a similar source searching on the Internet: Who in fact invented photography, Niépce or Daguerre?

For more than one hundred and fifty years, it has been generally acknowledged, even in the least unfavorable writings to Daguerre that the discovery had to be attributed to Niépce, while leaving a mere improvement role to Daguerre. For our part, we have already denounced in various articles errors, inconsistencies, manipulations, doctored information, and, to speak frankly, plain lies, about this historical version. They were put forward by misguided or dishonest writers.

In an article published by the French daily, "Le Monde", dated December 23d, 1998, Michel Guerrin: le monde referred to a portrait of "Monsieur Huet" performed by Daguerre in 1837. In his paper, he reported the objections we had previously raised about this prevailing opinion in various articles published in the French periodical Vivre en Val d'Oise, and also in an "Open Letter" published in 1991.

In view of this fabricated and cleverly kept alive legend, we think that it is high time to undertake a contradictory and evidence based study.

In such a perspective, we cannot but express our utter disagreement with Jean-Louis Marignier's recent publications on the subject. Far from any malicious intentions, we want to stick to facts and facts alone. In the following lines we shall recall a few of them among the most significant ones.

J.L. Marignier published an article in the periodical "Pour la Science" (Feb. 1997, p. 38-39) expounding his experimental work on contact trials which he had performed in 1989. Regretfully, he did not mention nor comment the conditions surrounding these trials, leading to think they had been made with a "camera obscura". Obviously, such reporting on his experimental work lacks in evidence production, since he gives to think these results may be obtained through Niépce's method.

Furthermore, as a kind of conclusion (p. 427) of his book (2) dedicated to the man from Chalon-sur-Saône, J.L. Marignier expresses his criticism on Daguerre's remarks about Niépce's process. He is of the opinion that they are unjustified. He does not specify, however, on which grounds he is entitled to make such comments. Let us quote J.L. Marignier's own words on the subject: "In his manual, the Director of the Diorama (Daguerre) published 'A Note about Niépce's heliography' making annotations about what he considered erroneous statements. His sole objective was to deprecate the contribution of the inventor from Châlon-sur-Saône". Those lines are mutually contradictory with what he had published earlier in the periodical "Pour la Science" in which he makes the same comments as Daguerre about Niépce's trials, i.e. "the non feasibility of picture etching with an acid the trials he had made with a camera obscura".

If such methods were to go unchecked, it would be all too easy to write a story according to one's own convenience. Let us stress that these are but a few examples of methods that we disapprove of all the more that, to our dismay, those views are expressed by a CNRS (Centre National de Recherche Scientifique) researcher.

In the same periodicals or in various Internet sites under the influence of what we must call "the Niépce clan", the same author goes one step further. He attributes without a shred of evidence to both Niépce and Daguerre, associates for a time, the invention of a process involving the use of a lavender essence residue as the sensitive layer. In fact, Daguerre achieved this breakthrough alone. The latter not only discovered the reactive capacity of this material but also revealed the image with white petroleum fumes. The invention of this process represents Daguerre's contribution in his partnership contract with Niépce.

Under the terms of the contract, he was precisely in charge of "discovering a resin or a hydrocarbon (bitumen) endowed with enhanced sensitivity to light". That is precisely what we indicated in 1989, and the first to do so, in a paper published in "Les Annales de la Société L.J.M. Daguerre", and later on in 1991 and 1999 in other articles published in the magazine: "Vivre en Val d'Oise".

In reference to this process, Isidore Niépce (Nicéphore's son) wrote in a libel against Daguerre the following lines: "No longer was Daguerre initiated in Mr. Niépce's process that he took an active part in furthering its development: he replaced Judea bitumen used by my father by a lavender oil residue. It proved to be an advantage in terms of layer whiteness and greater sensitivity to light action". This process is not physautotype but the physiotipe.

In our own trials, we showed evidence that there was no latent image in Niépce's process, and stated so in the n°5 issue of "études Photographiques".

Determined to make his point in attributing the latent image discovery to Niépce, Jean-Louis Marignier finds its very concept in the use of acids: "But acids are not decomposed by light, and again it is a failure. This last research work enables Niépce to grasp that it is not necessary to use a compound whose transformation is directly perceived by the eye; he understands that a change of chemical properties due to the action of light, even if invisible, may bring about the image appearance in the course of a subsequent reaction".

If we turn to the publications of the time, however, we may read for instance the following statement:

* "...light also acts chemically on compounds which explains that whenever exposed to light some acids are decomposed" (1800). The decomposition of acids was indubitably an established fact. [Fourcroy ]

* "When nitric acid is exposed to daylight for a period of time, it soon starts turning yellow or red " (1816), a scientific fact that Niépce must have known since he was reading chemistry treatises as part of his research work. [Thénard]

In the above-mentioned experiment, Niépce conducted his trials with chlorine, an element which at the time was wrongly considered to be an acid compound containing oxygen (oxidized muriatic gas or oxidized muriatic acid). This greenish-yellow gas has bleaching properties.

Niépce's comments on the subject are self speaking (June 16th 1816): "oxidized muriatic acid is the only one that might be used; however, it is decomposed under light action only in the presence of water It etches clearly and distinctly the calcareous stone I shall therefore endeavor to prepare such a stone instead of paper, and a colored picture should then be engraved. I shall immerse it for some time in hot water, and afterwards I shall put it in contact with oxidized muriatic acid I assume that under those conditions, I shall obtain a decisive result if, as may be surmised, this acid is decomposed by light, and also if, in all likelihood, its dissolving activity is modified under such experimental conditions".

In fact, what was called at the time "oxidized muriatic acid" is not an acid at all, but when put in contact with the hydrogen fraction of the stone contained water, it is transformed under the light action into hydrochloric acid that in turn etches the stone surface.

In this particular application, Niépce's explanations are unambiguous. "Through this procedure the modification of chlorine under light action and the etching on stone take place simultaneously". The result is therefore visible. In no case can this procedure be considered to lead to a latent image.

Daguerre's process is quite different. In a first phase the information is recorded in silver iodide; it remains invisible and stable. Only, in a second phase, through another chemical reaction, is the image revealed. It is the very principle of the latent image.

In challenging this legend, we mean to denounce certain biased methods that, for the past 150 years, have led people to regard Niépce as the inventor of photography, and downgrade Daguerre to the rank of an usurper.

(1) With the scientist Chevreul, friend to Niépce de Saint-Victor (which explains a lot) disinformation will enter the Académie des Sciences. [Compte-rendu de l'Académie des Sciences, tome 73, année 1871]

(2) "Niépce: l'invention de la photographie", éd. Belin, 1999.

* obligatory mention:title and author