1839 and the Many Inventors of Photography

Between January 1839 and the summer of 1840, at least nine people in five countries claimed, or could have claimed, to have made photographs. They were not copying each other; most of them had no idea the others existed. Something had changed, and it was not the chemistry, which had been sitting on the shelf for decades. This page is about what changed, who was standing in the room when it did, and why the question people always ask about it is the least useful one available.

The question that produces a bad answer

Helmut and Alison Gernsheim put the real puzzle better than anyone: photography could have been invented centuries before it was, and “the circumstance that photography was not invented earlier remains the greatest mystery in its history.” Both ingredients were old. A camera obscura with a convex lens dates from the sixteenth century, as the camera obscura page sets out; the darkening of horn silver in sunlight was in print in 1614 and proved to be light rather than heat in 1727, on the silver salts page. Anyone from about 1620 onwards had the parts.

Two answers to the Gernsheim question, and this course thinks both are right.

Nobody wanted to. Geoffrey Batchen’s argument, which Mike Ware summarises, is that what appears around 1800 is not a new technology but a new desire — a “will to photograph” that simply was not present in society before. Wanting a permanent image of what a lens throws on a wall is a historically specific want, and it arrives with a particular class of educated, leisured, image-hungry amateurs.

And the physics was against them. Ware adds two obstacles a modern reader underestimates. The first is psychological: a print-out image is a negative, and a striking number of the pioneers found that disqualifying. Samuel Morse recalled abandoning his own experiments because, “finding that light produced dark, and dark light, I presumed the production of a true image to be impracticable, and gave up the attempt.” Hercules Florence wrote in 1833 that light drew the objects in his camera obscura “but with the imperfection that the lighter parts become darker and vice-versa.” Ware notes that Herschel too was uncomfortable with negatives and spent years chasing positive-working processes. Talbot was the exception, and Ware quotes his Notebook M of 1835 to show why: he had already seen that a transparent first drawing could print a second one with the tones reversed back.

The second obstacle is arithmetic. Only a small fraction — Ware puts it between a hundredth and a thousandth — of the light a subject scatters gets through a lens onto the plate. A contact photogram therefore takes a hundredth to a thousandth of the camera exposure, which is why every one of these people made photograms years before they made a camera picture, and why print-out camera work sat at the edge of the possible until somebody found development.

What actually changed

Four things became available at once, and only the fourth is new in 1839.

A material sensitive enough, which for a camera means a developed latent image rather than a printed-out one. Daguerre had it from 1837 with mercury vapour; Talbot from September 1840 with gallic acid. Kodak’s own teaching primer put the size of the gap plainly: the earliest photographic material was silver chloride paper darkening under light, and its sensitiveness was far too slight to use that way in a camera.

A way to stop the picture changing. Herschel’s thiosulfate, connected to photography in January 1839 and published on 14 March.

A support and a geometry, which had existed for two centuries.

Publication. This is the one that dates the medium. Talbot’s own verdict, written in The Pencil of Nature, concedes the priority argument and then makes exactly this point: though the daguerreotype was not entirely new and his own labours had been anticipated by Wedgwood, “the improvements were so great in all respects, that I think the year 1839 may fairly be considered as the real date of birth of the Photographic Art, that is to say, its first public disclosure to the world.”

Nothing in that sentence is about chemistry. He is saying that a process nobody has told anybody about is not yet an art, and he had four years of secret pictures to prove it.

The eighteen months

Date	Who	What
7 Jan 1839	Arago, Paris	Announces Daguerre’s invention to the Académie des sciences, without the method
25 Jan 1839	Faraday, London	Shows Talbot’s photogenic drawings at the Royal Institution
29 Jan 1839	Herschel, Slough	First fixes a photograph with thiosulfate; shows Talbot on 1 February
31 Jan 1839	Talbot, London	Reads his first paper to the Royal Society; no working details
1 Feb 1839	Kobell and Steinheil, Munich	Their claim to fixed silver chloride images on paper appears in the Nationalzeitung
5 Feb 1839	Bayard, Paris	Shows early specimens of his own process to Desprets
21 Feb 1839	Talbot, London	Discloses the method: photogenic drawing paper, fixed with salt or potassium iodide
25 Feb 1839	“J. M.”, Berlin	First appearance of “photograph(y)” in print, in the Vossische Zeitung
9 Mar 1839	Morse, Paris	Writes to his brothers describing Daguerre’s process and his own abandoned attempt
14 Mar 1839	Herschel, London	Reads “Note on the Art of Photography” to the Royal Society: the hyposulphites
17 Apr 1839	Fyfe, Edinburgh	Describes a direct-positive method to the Society of Arts
Apr 1839	Reade, London	Exhibits pictures made with nutgall-treated paper at the Royal Society
1839	Ponton, Edinburgh	Reports that bichromate of potash paper is photographic and fixes in water
24 Jun 1839	Bayard, Paris	Exhibits direct positive prints publicly
19 Aug 1839	Arago, Paris	Gives the full daguerreotype description at a joint session of two academies
11 Nov 1839	Bayard, Paris	Deposits a description of his process with the Academy, in a sealed letter
20 Feb 1840	Herschel, London	Reads the paper that introduces negative and positive
24 Feb 1840	Bayard, Paris	The process is finally published
16 Mar 1840	Arago, Paris	Reports to the Academy on the priority of the direct-positive process
23 Sep 1840	Talbot, Lacock	Invents the calotype: a developed latent image on paper
8 Feb 1841	Talbot, London	Patents it, No. 8,842
16 Jun 1842	Herschel, London	Reads the paper that names the cyanotype, chrysotype and their relatives
Oct 1843	Atkins, Halstead	Distributes the first fascicle of Photographs of British Algae
Jun 1844 – 1846	Talbot, Reading	The Pencil of Nature, six fascicles, twenty-four plates

Dates in this table come from Eder, Ware’s chronology, the two DNB notices and the museum sources listed at the foot of the page. Where they disagree, the disagreement is flagged below rather than smoothed over.

The claimants

Hippolyte Bayard, and the process that lost

Bayard (1801–1887) was a clerk at the Ministry of Finance who experimented after hours. The Getty Museum, which holds the second largest collection of his work, records that he began experimenting in January 1839 — the same month as both announcements — and invented the direct positive process on paper.

Eder describes what it was, and it is ingenious. Silver chloride paper is blackened all over in daylight, soaked in about 4 % potassium iodide, and exposed while still moist in the camera. Light now bleaches rather than darkens: iodine separates from the potassium iodide and attacks the blackened silver, so the bright parts of the scene come out bright. A positive, straight out of the camera, on paper, needing about an hour.

Its virtue is its defect. It is a positive, which is what everybody said they wanted — and because it is a positive, it cannot be printed from. Bayard’s process solved the third problem by abolishing it. The Getty’s summary of what happened next is brisk: his work was overshadowed by two more prominent figures with better connections.

⁇Bayard's 24 June 1839 exhibition

The show is very often described as the first public exhibition of photographs. Eder records the event — the pictures “were exhibited by Bayard in Paris, June 24, 1839, and were favorably mentioned in the French journals of July and August, 1839” — but not that description of it, and the course could not verify the superlative from the sources it read.

It is also awkward on its face. Eder himself notes that the Moniteur officiel of the same date carried a description of Bayard’s pictures; the DNB has Faraday showing Talbot’s photogenic drawings at the Royal Institution on 25 January 1839, five months earlier; and Talbot exhibited again to the Royal Society on 31 January.

What the course states. Bayard exhibited direct positive prints publicly in Paris on 24 June 1839 and was well reviewed for it. Whether that was the first public exhibition of photographs anywhere depends on what counts as an exhibition, and this page does not decide it.

Hercules Florence, in Campinas

The Getty Conservation Institute’s atlas puts Florence’s case in a single startling sentence: the oldest photochemically produced images on paper still extant appear to be pharmaceutical labels made by Hercules Florence in Brazil. Having no printing shop within reach, he scratched his label designs into dark varnish on flat glass and printed them by contact onto paper sensitised with silver and gold chloride. He began in 1832, and his surviving notebooks show good results in 1833–34. He devised a fixing method using urine. His notebooks describe camera obscura experiments and contain a drawing of his camera and copying frames, though no camera photographs have been located.

He published nothing. The atlas records that his photographic work was “virtually ignored by historians of photography” until the 1970s, when Boris Kossoy’s research recovered it.

⁇Florence's priority, and the word photographie

Ware reports, on Kossoy’s authority, a claim that Florence used the French word photographie in 1833 — six years before Wheatstone, Herschel or the Vossische Zeitung. Ware gives 1833; 1834 is also commonly quoted; and the Getty atlas, which does not discuss the word at all, dates Florence’s good results to 1833–34. The course could not settle the year from its sources, so it reports the claim with Ware’s date attributed rather than asserted.

The larger claim — that Florence should be counted an independent inventor of photography — rests on better ground: the Getty Conservation Institute, a tier-1 conservation source, states that his surviving labels appear to be the oldest photochemically produced images on paper still extant, and that his notebooks document the method. What he did not have is a reader. This page treats him as an independent inventor whose work influenced nobody else’s until Kossoy recovered it in the 1970s, and treats that as a fact about the history of communication rather than about him.

The direct-positive tangle: Lassaigne, Fyfe, Bayard, Verignon

Bayard was not alone even in his own method, and Eder’s account of the resulting quarrel is the most useful thing on this page for anyone who wants to see how a priority dispute actually goes.

On the day Bayard announced his process to the Academy, Verignon presented a similar one. Days later Lassaigne reminded the members that he had communicated the same thing a year earlier, in L’Écho du monde savant of 10 April 1839. Arago investigated and reported to the session of 16 March 1840 that the methods of Verignon and Bayard did not differ from Lassaigne’s. Meanwhile, in Edinburgh, Andrew Fyfe had described the same bleaching method to the Society of Arts on 17 April 1839, using paper prepared with silver chloride or phosphate, and Eder notes separately that Fyfe fixed his photographs with ammonia.

⁇Who invented the direct positive?

Four people, in two countries, with the same idea inside twelve months. Bayard showed specimens privately from February 1839, exhibited in June and deposited a sealed description in November. Verignon presented a similar process to the Academy on the day Bayard’s was published. Lassaigne claimed to have communicated it a year earlier, in L’Écho du monde savant of 10 April 1839. Fyfe described the same bleaching method in Edinburgh on 17 April 1839.

Arago, adjudicating for the Academy on 16 March 1840, found that Verignon’s and Bayard’s methods did not differ from Lassaigne’s. Eder, writing a century later, agrees on the criterion and extends the list: “If priority of publication of the process is to decide whose claim is valid, Lassaigne must be mentioned first, then Fyfe, and only then Bayard and Verignon.”

What the course states. On publication dates, Eder’s order. The course reports that order without endorsing publication dates as the right criterion, for the reason set out at the end of this page: they measure access to a learned society rather than who did the work.

Mungo Ponton, and a family the course will not perform

In 1839 Mungo Ponton reported that paper soaked in bichromate of potash is “powerfully and rapidly acted on by the sun’s rays”. Hunt’s Manual of Photography quotes his own description of it from the Edinburgh New Philosophical Journal, and this is the part that makes it interesting:

To fix it, all that is required is careful immersion in water, when it will be found that those portions of the salt which have not been acted on by the light are readily dissolved out, while those which have been exposed to the light are completely fixed on the paper.

That is a third answer to the permanence problem, and it is neither Herschel’s nor Talbot’s: light does not reduce a metal here, it makes an organic layer insoluble, so plain water separates the image from the rest. Niépce’s bitumen works in exactly that way, and the heliography page owns the distinction between the two families. The cyanotype’s wash arrives at the same convenience by a different route — there the image is a new insoluble pigment rather than a changed coating — and the difference is worth holding on to, because it is the difference between a resist and a picture.

Hunt is realistic about it: bichromate paper is not sensitive enough for the camera obscura, but it answers well for copying prints and dried plants, and its recommendation is cost — two shillings a pound against five shillings an ounce for silver nitrate.

⁇Who found the light-sensitivity of chromates?

Eder’s own chapter heading credits the chromate processes to Ponton in 1839, and then immediately complicates it. Vauquelin had found in 1798 that chromic acid forms a carmine-red silver salt that darkens in light — but that is a silver compound, so the reaction belongs to silver photochemistry. Eder gives the real precedent to Suckow, who in 1832 found that chromate salts mixed with organic substances are light-sensitive without any silver: “He must be recognized as the first discoverer of this light reaction.” Ponton’s contribution, on Eder’s reading, is the first application of it to printing on paper — and Eder adds that Ponton’s own explanation of the chemistry “was quite incorrect”, and that he missed the far more important sensitivity of dichromate mixed with gelatin or gum, which Talbot patented on 29 October 1852.

What the course states. Suckow, 1832, for the effect; Ponton, 1839, for the photographic application; Talbot, 1852, for dichromated gelatin. Where a source says simply “Ponton discovered it”, read that as shorthand for the middle claim.

The whole chromium(VI) family — carbon printing, gum bichromate, photogravure, dichromated gelatin — descends from that observation, and it is also the reason the family sits where it does in this course’s safety scheme. Potassium dichromate’s aggregated GHS classification on PubChem is severe enough that a home procedure is not on offer; Part XXVI carries the assessment and the argument.

Joseph Bancroft Reade, Kobell and Steinheil, and Morse

Three shorter cases, each of which fails in a different and instructive way.

Reade exhibited pictures at the Royal Society in April 1839 made on paper soaked in a decoction of nutgalls and then silver nitrate, used moist. The claim regularly made for him is the discovery of development. Eder rejects it on the ground that Reade treated the tannin purely as an accelerator of ordinary blackening and did not recognise a latent image at all, and adds that his images were made with silver nitrate and gallic acid, not with a silver halide. Talbot’s page sets the dispute out in full, including Reade’s second, separate claim about hypo, which Eder says cannot now be verified.

Kobell and Steinheil, in Munich, asserted in the Nationalzeitung of 1 February 1839, with a fuller description on 9 April, that they had made and fixed silver chloride images on paper. Eder’s dismissal is one line long and worth reading twice: “this has no more to do with daguerreotypy than does the claim of the Reverend Hoffmeister.” He is not saying they did nothing; he is saying that the claim being staked was for a different invention from the one being announced.

Morse is the clearest case of all, because he wrote down why he stopped. He was in Paris to sell his telegraph, met Daguerre in the winter of 1838–39, was shown the process in confidence, and reported it home on 9 March 1839. In the same letter he recalled his own attempts at Yale, years before, to fix the camera obscura image on paper dipped in silver nitrate: he got different degrees of shade from different degrees of light, and gave up on finding that light produced dark. Morse had the material, the instrument and the idea, and abandoned them over the tonal inversion that Talbot tolerated.

⁇Two claimants this course does not adjudicate

Friedrich Gerber, of Bern, is regularly named among the 1839 claimants. The course found no account of his work in the sources it read and therefore says nothing about it beyond recording that the claim exists and that this page did not verify it.

Robert Cornelius, in Philadelphia, is as regularly named as the maker of the first photographic portrait in late 1839. The daguerreotype page owns that dispute, sets out Eder’s preference for Draper in the autumn of 1839, and declines to adjudicate. Nothing here overrules it.

The three problems, scored

The framework is the course’s own, as the part overview says. What follows is not a scoreboard; it is six one-line judgements with their reasons attached, and each of them is argued on the page that owns the process.

Process	Sensitivity	Permanence	Reproducibility	Hazard
Heliography (1826)	Failed. Bitumen has no amplification step: what light did is all you get, so a camera view took hours or days	Solved, and trivially. The image is a hardened varnish; the solvent removes the rest	Solved for engravings, by etching the plate and printing it in ink; not for camera views	Lavender oil and petroleum solvents; the etching used acid
Daguerreotype (1839)	Solved, decisively. Mercury vapour develops an exposure too short to see, cutting minutes to seconds by 1841	Solved. Hot salt first, hyposulphite of soda within the year, gilding from 1840	Not solved, and not solvable. The plate in the camera is the finished object; no negative exists at any stage	Mercury vapour, bromine, iodine. Level D: studied, never performed
Photogenic drawing (1834–39)	Poor. Printing-out only, an hour or more in the camera on a good day	Not solved: salt and iodide stabilise rather than remove, and iodide-fixed prints fade in the dark	Solved in principle from 1835: a translucent negative prints any number of positives	Silver nitrate, handled wet. A reading page here; practised in Part XXII
Calotype (1840)	Solved. Gallic acid develops a latent image in silver iodide; about a hundredfold over printing out	Solved once hypo is used; Talbot’s own bromide fixing was a compromise he preferred aesthetically	Solved in practice. Talbot: the number of copies “appears to be almost unlimited”	As above, plus gallic and acetic acid
Bayard direct positive (1839)	Poor: about an hour in the camera	Partly. The image is bleached silver; contemporaries found the prints fragile, and the Getty keeps them in the dark	Abolished, not solved. A direct positive has no negative to print from	Silver chloride and potassium iodide
Cyanotype (1842)	Poor, and it does not matter: a contact print takes minutes, and no camera use was ever serious	Solved by omission. The image is an insoluble pigment and the sensitiser is soluble, so water finishes it	Solved for contact printing from a negative or an object; it is a printing process, not a capture one	Level A with pre-coated paper; see the assignment

Read the third column down the table and the history of the next hundred and fifty years is in it. The process with the best pictures could not be copied. The process with the worst pictures could.

Three axes cut across that table, and they are not the same axis three times.

Direct positive against negative-positive is about whether an intermediate exists. A direct positive gives you the finished picture in the camera and nothing to print from; a negative gives you something ugly and useful. The daguerreotype and Bayard’s process are on one side, Talbot and Niépce’s engraving copies on the other, and the side with the intermediate is the side that could become an industry.

Printing-out against developing-out is about where the energy comes from. Printing out spends light; developing out spends light to make a trigger and then spends chemistry. It is the difference between an hour and a second, and Reilly puts the exposure ratio at up to 100,000 to 1. Every process in the table except the daguerreotype and the calotype is a printing-out process, which is exactly why every one of them is a contact process too — you cannot enlarge onto a material that slow.

Metal against pigment is about what the picture is made of, and it decides how it ages. A silver image is a finely divided reactive metal in intimate contact with whatever else is in the paper, and it tarnishes, fades and sulfides; Prussian blue is an insoluble pigment that is indifferent to sulfur and vulnerable to alkali instead. Neither is simply more permanent than the other. They fail differently, and knowing which failure you have bought is worth more than a ranking.

The family tree, and who owns each branch

The two families are the Niépce page’s subject, and its table sets out what separates light reducing a metal salt from light hardening a coating. What this page adds is the descent: which branch each later part of the course is standing on.

Where the 1839-era processes lead

1. 1Silver printing-out — photogenic drawing, salted paper, albumen, collodion POP — Part XXII
2. 2Silver developing-out — daguerreotype, calotype, collodion, dry plate, all modern film — Parts IV, V, XIII
3. 3Iron reduction (siderotype) — cyanotype — Part XXI; argentotype to kallitype and Van Dyke — Part XXIV; platinum and palladium
4. 4Bitumen and photoresists — heliography, photogravure, and every microchip made since
5. 5Dichromated colloids — Ponton 1839, Talbot 1852; carbon and gum printing — Part XXVI. Chromium(VI): the hazard branch

Only the descent is drawn; the mechanism that splits the two families belongs to the heliography page, which owns it. Every branch here is still practised somewhere, and the bitumen branch is by far the largest industry of the five.

What a roll of film owes to 1839

Load a roll of black-and-white film today and you are holding five inheritances, each traceable to a named person in this part.

The thing	Where it comes from	The evidence
A latent image, developed	Daguerre, 1837; Talbot on paper, September 1840	Ware calls development an extraordinary fluke of silver halide chemistry, amplifying the effect of light more than a millionfold; nothing else in Part I has it
Fixing with thiosulfate	Herschel, January 1839	The reagent and the reasoning are unchanged; modern rapid fixers substitute the ammonium salt for the sodium one, and Part XI weighs the two
Negative to positive	Talbot, 1835 as an idea, 1841 in practice; the words from Herschel, 1840	Herschel’s own argument for the terms is that multiplied facsimiles are what make publication possible
Halide sensitisation	Talbot’s excess silver, 1834; the shift to bromide and iodide through the 1840s	Talbot’s 21 March 1839 note on silver bromide paper is the first step of a road that ends in the modern emulsion
A binder that holds crystals off the fibres	Not from 1839 at all	Photogenic drawing puts the silver in the paper; the gelatin emulsion arrives in 1871 and is Part V’s

The gap in the last row is the honest part of the table. Four fifths of a modern film is Part I’s; the fifth that makes it manufacturable is not.

Reading three photographs

Do this with a screen and three open-access museum collections, and give each object a short paragraph.

Find a daguerreotype, a salted paper print from a calotype negative and a cyanotype, and compare them under: detail, tonal scale, surface, colour, permanence and uniqueness. Note the last two carefully, because they are the ones a reproduction hides. The daguerreotype is a single object that has to be sealed behind glass because its surface is the image. The salt print is one of an edition, matte and sunken into the paper, and the Getty atlas notes that untoned ones run from light brown to reddish brown; many of the survivors have faded, and the Talbot page explains why. The cyanotype is one of an edition too, and of the three it is the one most likely to look exactly as it did in 1843 — unless somebody mounted it on buffered board.

Then answer the question the exercise exists for: which of these three would you have chosen to make in 1841, and for whom? A portrait studio and a botanist and a publisher give different answers, and all three answers are defensible.

Why the question is wrong, and what to ask instead

“Who invented photography” fails for three separate reasons, and it is worth keeping them apart.

It assumes there is one thing. There is not. There is a sensitive material, a development step, a fixing step, an optical system, a negative-positive workflow and a public disclosure, and no single person supplied more than two of them. Talbot had the workflow and the paper developer; Daguerre had the plate and the vapour developer; Herschel had the fixer and the vocabulary; Niépce had the first camera image that still exists and no way to keep making them.

It assumes invention is an event. Ware’s chronology of Talbot alone runs from June 1834 to 1846 and contains at least a dozen moments that could be called the invention. Herschel’s cyanotype has a diary entry with a date on it, 23 April 1842 — and Ware still prefers discovered to invented for it, because Herschel washed a salt onto paper to see what would happen and something did.

It rewards the wrong evidence. Priority disputes are settled by publication dates, which measure access to a learned society. Lassaigne beats Bayard because he got a note into a journal. Florence, who may have been years ahead of everyone, loses entirely, because Campinas had no journal and he wrote in a notebook. Eder’s own adjudications keep running into this, and so does every historian’s.

Better questions, all of which have answers:

• What problem was this person actually trying to solve? Schulze wanted a luminous stone. Herschel wanted to probe the spectrum. Niépce wanted to copy engravings without an engraver. Talbot wanted to draw. Not one of them set out to invent photography, and their processes bear the marks of what they did want.
• What did they demonstrate, and what did they merely observe? Schulze ran a heat control; Scheele ran an ammonia test; Herschel ran the two-stage experiment that located the photochemistry in the iron. Those are different acts from noticing that something went dark.
• What could someone else do with it afterwards? This is the question 1839 answers and 1802 does not, and it is why Talbot dated the birth of the art to disclosure rather than to discovery.

!House style for a contested date

You have now met the pattern several times, and it is the pattern the rest of the course uses. When a date, an attribution or a mechanism is disputed, this course does four things and no more: it names the disagreement, it names who holds each position, it says which the course uses, and it says why. It does not average the positions, it does not pick the most-cited one, and it does not quietly choose and move on.

The corrections established in Part I, which every later page must respect: Schulze is 1727, not the widely repeated 1717 or 1719, neither of which this course could source. Fabricius is 1565 and recorded nothing about light, that claim being traceable to an error in Arago’s 1839 report. Bunsen and Roscoe’s photochemical investigations are 1855–1859, not 1862. And on this page: Suckow, 1832, for the light-sensitivity of chromates without silver, with Ponton’s 1839 work as the first photographic application.

The bridge out of Part I

Everything after 1846 belongs to a later part, which owns the evidence for it. The point of listing them here is that you should be able to see, from where you are standing, what each one is answering.

Year	Event	The problem it addresses	Owner
1847	Niépce de Saint-Victor: albumen on glass	A support with no fibres, so the negative is sharp	Part XXIII
1850	Blanquart-Evrard: albumen paper	A smoother, glossier positive surface than salted paper	Part XXIII
1851	Archer: the collodion wet plate	Camera speed on glass, out of patent, and it displaces both 1839 processes	Part XXVI
1852	Talbot: photoglyphic engraving	Photography back into printer’s ink, from Ponton’s dichromate	Part XXVI
1855–1859	Bunsen and Roscoe: photochemical investigations	Reciprocity: exposure as the product of intensity and time	Parts XIII and XIV
1871	Maddox: the gelatin dry plate	A binder that can be manufactured, stored and sold	Part V
1873	Vogel: dye sensitisation	Making a silver halide respond to light it cannot absorb	Part IV
1888	The Kodak camera	Photography without a photographer’s knowledge	— this course does not follow it
1890	Hurter and Driffield	Measurement: density, exposure and the characteristic curve	Part XIII
1906	Panchromatic plates	Response across the whole visible spectrum	Part IV
1938	Gurney and Mott	A theory of the latent image, ninety-nine years after it was first used	Part IV

Each of those dates is that part’s to verify, and none of them is asserted as established here beyond the two this course has already fixed: Bunsen and Roscoe are 1855–1859, not 1862, and Talbot’s dichromated-gelatin patent is 29 October 1852.

What you have, and where each piece goes

Part I ends with three objects and a habit.

A camera obscura, which becomes the body of the pinhole camera in Part VI and the reason you already know what an image is before any chemistry acts on one.

An unfixed silver photogram, in two halves — one that has been dying in room light and one sealed in an envelope. Part XI opens by asking for both, and by then you will be able to say precisely what the fixing bath would have removed and what it would have cost.

A cyanotype photogram, which is permanent, and which Part XXI asks you to make again on paper you have coated yourself, so that the two can be compared.

And the habit: one line per exposure, dated. Part II turns it into a laboratory record with a template and a purpose, but the discipline is the one you have been practising since the first sheet went out in the sun.

Recap

• The materials for photography existed from about 1620. What appears around 1800 is the wish, and what appears in 1839 is disclosure.
• Ware adds two reasons for the delay that are not about wanting: the negative image put several pioneers off entirely, and camera exposures are a hundred to a thousand times longer than contact exposures, which kept print-out camera work at the edge of the possible.
• At least nine people had a claim in 1839–40. Bayard’s direct positive worked and could not be copied; Florence was years early and published nothing; Lassaigne, Fyfe, Bayard and Verignon independently found the same bleaching process inside a year; Reade had gallic acid but not the latent image; Morse gave up over the tonal inversion.
• Ponton’s 1839 chromate paper is a third answer to permanence — light makes a layer insoluble, and water removes the rest — and the seed of the chromium(VI) family the course studies but does not perform.
• Scored on the three problems, the daguerreotype wins the first two outright and loses the third absolutely; the calotype is second on all three and first where it counts.
• A modern film inherits four things from this decade and one from 1871: the latent image and development, thiosulfate fixing, the negative-positive workflow and halide sensitisation, but not its gelatin binder.
• “Who invented photography” assumes one thing, one moment and one kind of evidence, and each assumption fails. Ask what problem someone was solving, what they demonstrated, and what anyone else could do with it afterwards.

Check your understanding

Question 1. Hippolyte Bayard's 1839 process gave a positive image directly in the camera, on paper. Judged against the three problems this part is organised around, what is its decisive weakness?

• It was too slow, requiring about an hour in the camera
• The image was not permanent, because bleached silver continues to change
• A direct positive has no negative, so it cannot be printed from: it does not solve reproducibility, it removes the possibility
• It used potassium iodide, which was more expensive than silver nitrate

Show the answer and why

Answer: A direct positive has no negative, so it cannot be printed from: it does not solve reproducibility, it removes the possibility

The hour-long exposure was ordinary for 1839 and permanence was a problem everyone had. What makes Bayard structural rather than merely unlucky is the third column: he made the object everyone said they wanted, a positive straight from the camera, and in doing so gave up the only property that let paper photography beat the daguerreotype. The daguerreotype has the same defect and far better pictures. Bayard's process had neither advantage, which is why a beautifully solved problem can still be the wrong problem.

Question 2. Mungo Ponton's bichromate paper is fixed by immersion in plain water. Which other process in this part works on the same principle, and what is the principle?

• The daguerreotype: light changes the surface, and the unchanged part is removed chemically
• Heliography: light makes a layer insoluble, and a solvent washes away what light did not act on
• The calotype: light creates a latent image that a developer amplifies
• Photogenic drawing: light reduces silver, and excess halide deactivates the rest

Show the answer and why

Answer: Heliography: light makes a layer insoluble, and a solvent washes away what light did not act on

Bitumen of Judea and dichromated colloids belong to the same family: light does not reduce a metal, it changes the solubility of an organic layer, so the picture and the unwanted material differ in solubility and one wash separates them. That is why both fix so easily and why neither amplifies - what light did is all you get. The heliography page sets out the split between the two families in full. The cyanotype reaches the same convenience by a different route: there the image substance is an insoluble pigment and the sensitiser is soluble.

Question 3. Samuel Morse abandoned his own photographic experiments years before 1839. What stopped him, and why is it historically interesting rather than merely unlucky?

• He could not fix the image, and concluded no fixer existed
• His paper was too insensitive for a camera, and he had no way to make it faster
• He got dark where the scene was light, judged a true image impracticable, and stopped: the same tonal inversion Talbot accepted and built on
• He was distracted by the telegraph and never returned to it

Show the answer and why

Answer: He got dark where the scene was light, judged a true image impracticable, and stopped: the same tonal inversion Talbot accepted and built on

Morse wrote it down in a letter of 9 March 1839: he could produce different degrees of shade from different degrees of light, "but finding that light produced dark, and dark light, I presumed the production of a true image to be impracticable, and gave up the attempt." Ware collects several pioneers who reacted the same way, including Florence, and argues that a psychological intolerance of the negative image is a real reason photography arrived when it did. Talbot's Notebook M of 1835 shows him doing the opposite: seeing that a transparent negative would print a positive, and building the medium on it.

Question 4. Eder concludes that on publication dates the direct-positive process belongs to Lassaigne, then Fyfe, then Bayard and Verignon. What does that adjudication actually measure?

• Which of them first performed the experiment
• Which of them had the best version of the process
• Which of them got a description into print first, which depends on access to a journal or a learned society
• Which of them was first to fix an image permanently

Show the answer and why

Answer: Which of them got a description into print first, which depends on access to a journal or a learned society

Priority by publication measures publication, and publication measures access. That is a reasonable rule for settling disputes among people who all had access, and a very poor one for judging who did something first: Hercules Florence was probably years ahead of every name in that list and loses completely, because he was in Campinas, published nothing and was ignored by historians until the 1970s. Knowing what a criterion measures is the difference between using it and being used by it.

Question 5. A modern black-and-white film inherits four things from the 1839-46 decade. Which of the following is NOT one of them?

• A latent image amplified by chemical development
• Fixing by dissolving the residual halide in thiosulfate
• A gelatin emulsion holding the crystals in a coating above the support
• The negative-positive workflow, one original giving many prints

Show the answer and why

Answer: A gelatin emulsion holding the crystals in a coating above the support

The binder is the one that is not from this decade. In photogenic drawing and the calotype the silver salt is formed inside the paper fibres, with the sizing as its only binder; the gelatin emulsion coated on a separate support is Maddox's, in 1871, and Part V owns it. The distinction matters practically: silver in paper gives a matte, sunken image whose sharpness is limited by the fibres, and silver in an emulsion layer gives the sharp, glossy, machine-coatable material the twentieth century ran on.

Question 6. Talbot wrote that 1839 "may fairly be considered as the real date of birth of the Photographic Art, that is to say, its first public disclosure to the world" - even though he had been making photographs since 1834 and Niepce since 1826. What is the argument in that sentence?

• That the 1839 processes were the first to produce permanent images
• That a process nobody has disclosed is not yet an art, whatever pictures it has made in private
• That the daguerreotype and the calotype were the first processes fast enough for a camera
• That priority should go to whoever publishes first

Show the answer and why

Answer: That a process nobody has disclosed is not yet an art, whatever pictures it has made in private

He is not conceding priority - the same passage insists that Wedgwood anticipated him and that the daguerreotype was not entirely new. He is drawing a distinction between having a process and there being a medium. Niepce's heliography died with him partly because he kept it close; Florence's work waited a century and a half for a historian. What 1839 supplies is not chemistry but circulation, which is also why this course keeps saying which parts of a claim were published, when, and to whom.

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The pages of this part

Part1 of 28Level1 — FoundationPages10Estimated time11.7 hoursHighest safety levelLevel D

0 / 10 lessons in this part completed

• BuildThe Camera Obscura: An Image Without ChemistryA150 min
• LessonSilver Salts and Light: Schulze to Ritter45 min
• LessonWedgwood, Davy and the Problem of Permanence40 min
• ExperimentExperiment: The Image That Would Not StayA120 min
• LessonNiepce and Heliography: Light That Hardens40 min
• LessonDaguerre and the Daguerreotype: A Mirror With a MemoryD45 min
• LessonTalbot: Photogenic Drawing, the Calotype and the Negative-Positive Principle50 min
• LessonHerschel: Hypo, Prussian Blue and the Words of Photography45 min
• AssignmentAssignment 1: A Botanical Cyanotype Photogram, After AtkinsA120 min
• Lesson1839 and the Many Inventors of Photography45 min