The camera was a simple brass device, not much bigger than a fist. Inside it sat small pieces of X-ray film, and across a small opening in the front, Rosalind Franklin and her student Raymond Gosling fixed a slender fibre drawn from a solution of DNA. They aimed a fine beam of X-rays into that hole for hours or days to make each image. In the spring of 1952, at King’s College London, one of those exposures produced the sharpest diffraction pattern they had seen. It was also flawed: the pattern sat off centre and was cut short at one edge, because the film mount inside the camera had slipped.
That image was Photograph 49. Franklin started a new exposure of the same sample on the same day she saw it, and the new one became Photograph 51, the most famous picture in the history of molecular biology. For more than half a century the standard story has held that Franklin did not understand what her own picture showed. A paper published on 5 October 2026 in the Journal of the History of Biology argues the opposite, and it rests its case on the forgotten photograph that came first.
The standard story belongs largely to James Watson. In 1953, according to the version he told, Maurice Wilkins showed him one of Franklin’s DNA photographs at King’s, and Watson had a revelation. “The instant I saw the picture my mouth fell open and my pulse began to race,” he wrote. In his 1968 autobiography, The Double Helix, he described the photograph as his moment of insight: “The black cross of reflections which dominated the picture could only arise from a helical structure.”
Others repeated the idea that Franklin had looked at the same pattern and missed its meaning. Horace Judson, author of what remains the best-known journalistic account of the discovery, wrote in 1979 that “The pattern shouted helix,” yet for nearly ten months Franklin “turned her back on her own discovery of the B structure of DNA and her own best evidence that [it] was helical.” Franklin’s biographer Brenda Maddox called the photograph “the clearest picture ever taken of the B form of DNA” and described Franklin putting it aside to return to the puzzle of the A form.
The new paper is written by a historian of science and a crystallographer: Alistair Sponsel of the Science History Institute in Philadelphia and Brian Sutton of King’s College London. Their answer to Judson is direct. Photograph 51 shouted “helix” so clearly, they write, because Rosalind Franklin intended it to.
Part of the reason Watson’s version lasted is a gap in the record. Franklin’s laboratory notes were usually thorough and meticulous, but they say little about Photograph 51. Sponsel and Sutton turned to the earlier image instead and found that Franklin had made extensive notes about Photograph 49, despite its cosmetic defect. In their reading, she knew that the earlier photograph had revealed a helix, the very insight Watson later claimed for himself, and that is precisely why she made a second, more refined version. Photograph 51, they conclude, was taken specifically for publication. It was not, as some accounts have held, an experimental shot that Franklin thought unimportant.
The reshoot fits what colleagues have said about how she worked. Franklin “was an experimental perfectionist,” says the crystallographer Elspeth Garman. A photograph with a slipped film mount and a truncated edge was good enough to tell Franklin something. By this account, it was not good enough for her to show anyone else.
Why, then, did she not rush to publish? Sponsel and Sutton think her notes and actions explain that too, and they point to a report she wrote in February 1952 that laid out her scientific goals. DNA came in two forms, A and B. By the end of 1951 it was generally accepted at King’s that the B form was a helix, but after Franklin recorded an asymmetrical image in May 1952, she became unconvinced that the A form was one. In July 1952, as a practical joke on Wilkins, who often said both forms were helical, she and Gosling wrote a funeral notice announcing “the death, on Friday 18th July 1952 of DNA helix (crystalline)” and expressing the hope that Wilkins would “speak in memory of the late helix.”
Her method was slow by choice. Throughout 1952 she and Gosling applied a long, labour-intensive mathematical analysis to their X-ray pictures, and Franklin was firmly against building theoretical models ahead of the data. “We are not going to speculate, we are going to wait, we are going to let the spots on this photograph tell us what the [DNA] structure is,” she said.
The spots were moving her toward the answer. Her notebook shows that by February 1953 she had thought of a helical structure for the B form but was unsure of the number of strands, writing: “Evidence for 2-chain (or 1-chain helix).” Aaron Klug, who examined her papers after her death, at first believed she had not been convinced of the double helix until she learned of the Cambridge model. He later found an original draft of her manuscript, dated 17 March 1953, which made clear she had already reached the correct structure. News of the Watson and Crick model reached King’s the next day. Sutton himself had argued in 2023 that Franklin was close to the discovery: in early 1953, her notes show, she was explicitly considering a two-chain helix.
On 25 April 1953, Nature published three papers on the structure of DNA. Watson and Crick’s article acknowledged Franklin only in a footnote, saying they had been “stimulated by a general knowledge of Franklin and Wilkins’ ‘unpublished’ contribution.” Under a deal between the two laboratory directors, papers by Wilkins and by Franklin, with their X-ray data, were printed second and third in the same issue, seemingly only in support of the model. Watson and Crick themselves later said that without Franklin’s data, “the formulation of our structure would have been most unlikely, if not impossible.”
Franklin died of ovarian cancer in 1958, aged 37. The 1962 Nobel Prize in Physiology or Medicine went to Crick, Watson and Wilkins; the prize is never awarded after death. It was not until 1999 that Watson said “the Franklin photograph was the key event,” Garman writes. When The Double Helix appeared, even his co-laureates objected. Crick wrote to Watson that the book was misleading and in poor taste, and Wilkins said it was unfair to almost everyone in it except Watson.
The physicist and historian Robert Crease once sat through a series of lectures by Watson at Brookhaven National Laboratory. After the first talk, on the events around the discovery, there was time for one question. A woman raised her hand. “Dr Watson,” she asked, “I wonder if you could comment a little bit more on Rosalind Franklin’s contribution to the discovery of DNA.” Some in the audience applauded.