The camera was a simple brass device, not much bigger than a fist. Rosalind Franklin and her student Raymond Gosling fixed a thin fibre of DNA across a small opening at the front, with pieces of X-ray film inside. They then aimed a fine beam of X-rays at it for hours or days to make each image. In the spring of 1952, at King’s College London, one exposure produced the sharpest pattern they had ever seen. But it had a flaw: the film mount inside the camera had slipped, so the pattern was off centre and cut short at one edge.
That image was Photograph 49. On the same day she saw it, Franklin started a new exposure of the same sample, and that one became Photograph 51, the most famous picture in the history of molecular biology. For more than half a century, the usual story has said 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 bases its case on the forgotten photograph that came first.
The usual story comes mainly from James Watson. In his version, Maurice Wilkins showed him one of Franklin’s photographs at King’s in 1953, and Watson suddenly understood. “The instant I saw the picture my mouth fell open and my pulse began to race,” he wrote. In his 1968 book The Double Helix, he said the black cross in the picture could only come from a helical structure. Others repeated the idea that Franklin had seen the same pattern and missed its meaning. The writer Horace Judson wrote in 1979 that “The pattern shouted helix,” yet for nearly ten months Franklin had turned her back on her own discovery.
The new paper is by a historian of science, Alistair Sponsel of the Science History Institute in Philadelphia, and a crystallographer, Brian Sutton of King’s College London. Their answer to Judson is direct: Photograph 51 shouted “helix” so clearly because Franklin intended it to.
Part of the reason Watson’s story survived is a gap in the record. Franklin usually kept careful laboratory notes, but she wrote little about Photograph 51. So Sponsel and Sutton looked at the earlier image and found that she had made detailed notes about Photograph 49, despite its defect. In their reading, she knew that it showed a helix, the same insight Watson later claimed for himself, and that is exactly why she made a second, better version. Photograph 51, they conclude, was taken specifically for publication, not as an experiment she thought unimportant.
This fits what colleagues say about how she worked. Franklin “was an experimental perfectionist,” says the crystallographer Elspeth Garman. A photograph with a slipped film mount was good enough to tell Franklin something, but not good enough to show anyone else.
So why didn’t she hurry to publish? Sponsel and Sutton point to a report she wrote in February 1952 that set out her scientific goals. DNA came in two forms, A and B. By the end of 1951, people at King’s generally accepted that the B form was a helix, but in May 1952 Franklin recorded an image that made her doubt the A form was one. Her method was also slow on purpose. Throughout 1952 she and Gosling carried out a long, demanding mathematical analysis of their X-ray pictures, and she refused to build theoretical models before the data was ready. “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 leading her to the answer. Her notebook shows that by February 1953 she was thinking of a helical structure for the B form, though she was unsure how many strands it had. A draft of her paper dated 17 March 1953 shows she had already reached the correct structure. News of Watson and Crick’s model arrived at King’s the next day.
On 25 April 1953, Nature published three papers on the structure of DNA. Watson and Crick mentioned Franklin only in a footnote, and the papers by Wilkins and by Franklin, with their X-ray data, appeared after theirs in the same issue, seemingly only in support of the model. Watson and Crick later admitted 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. In 1962 the Nobel Prize in Physiology or Medicine went to Crick, Watson and Wilkins, and the prize is never given after death. Watson only said in 1999 that “the Franklin photograph was the key event,” Garman writes.
The physicist and historian Robert Crease once sat through a series of lectures by Watson at Brookhaven National Laboratory. After the first talk, about the discovery, there was time for one question. A woman raised her hand and asked Watson to say a little more about Rosalind Franklin’s contribution to the discovery of DNA. Some people in the audience applauded.