Archival research published in October 2026 shows that Rosalind Franklin deliberately captured Photograph 51 after using an earlier X-ray image to calculate key features of DNA’s helical structure. The findings challenge the long-standing narrative that she failed to grasp the significance of her famous images before James Watson saw them.
Franklin Calculated Helical Features From Photograph 49
Popular accounts of the discovery of DNA traced the definitive turning point to a visit James Watson made to Maurice Wilkins’s laboratory at King’s College London in 1953 according to Elpais for decades. In his 1968 memoir, The Double Helix: A Personal Account of the Discovery of the Structure of DNA
, Watson described how seeing a picture taken by Rosalind Franklin triggered an immediate realization as reported by Live Science.
That version of history held that Franklin’s lack of extensive notes on the iconic Photograph 51 indicated she missed what was right in front of her. But a study published in the Journal of the History of Biology by historian Alistair Sponsel and crystallographer Brian Sutton examines hidden details in her laboratory notebooks. The researchers show that Franklin had already made her primary structural calculations using an earlier, blemished exposure known as Photograph 49, taken on May 2, 1952.
That initial image suffered from a mechanical slip inside the camera that obscured part of the frame as detailed by Brightsurf.
Even so, Franklin extracted enough data to determine that the diffraction pattern matched a helix, calculating that the structure completed one turn every 3.4 nanometers with roughly 10 layers of bases per turn.
Franklin Purposely Retook Photograph 51
Rather than treating Photograph 51 as an accidental discovery whose meaning she overlooked, Franklin purposely retook the image to secure a clean, publication-quality record.
She took it because she wanted to get a really refined version,
said Alistair Sponsel, an oral historian and curator of life sciences at the Science History Institute in Philadelphia according to the Science History Institute. Sponsel noted that making the effort to photograph the exact same sample again was a sign she knew she had something really important on her hands.
Franklin viewed the two exposures as entirely different kinds of scientific records. Photograph 49 served as the experimental capture that yielded exciting new data, while Photograph 51 was intended as the polished showpiece noted Live Science. Her research priorities at the time also explain why she did not immediately rush to publish the second image. Her structured research plan involved characterizing two distinct forms of DNA: Structure A, which appeared more data-rich when dehydrated, and Structure B, the naturally occurring double helix captured in Photographs 49 and 51.
New Archival Collections Rewrote the History
The re-evaluation of Franklin’s work stems from archival materials newly accessible to researchers. Sponsel began re-examining the records in 2025 after the Science History Institute acquired the History of Molecular Biology Collection from the J. Craig Venter Institute reported the Science History Institute. That acquisition brought Franklin’s personal copy of Photograph 51, alongside extensive notebooks and correspondence, into a public collection. Sponsel subsequently connected with Brian Sutton at King’s College London, where Franklin and graduate student Raymond Gosling originally performed the experiments according to King’s College London archives.
Oxford crystallographer Elspeth Garman noted that retaking a significant sample is standard practice for an experimental perfectionist.
“Brian and I were each intrigued by the same features of Photo 51, and we wanted to gain a deeper understanding of why the image looked the way it did.”
Alistair Sponsel, oral historian and curator of life sciences at the Science History Institute
The Double-Helix Architecture Remained Unresolved
While the study establishes that Franklin recognized DNA’s helical nature from her work on Photograph 49, the authors clarify that she had not yet determined the full double-helix architecture on her own according to Elpais. By May 1952, she knew the molecule was a helix, but she had not yet resolved how two separate strands intertwined or how their chemical components paired.
That final step was completed when Watson and Crick used clues from the crystallographic images alongside chemical properties to build their physical model noted Elpais. Watson, Crick, and Maurice Wilkins ultimately shared the 1962 Nobel Prize in Physiology or Medicine reported Live Science, four years after Franklin died of ovarian cancer in 1958 at the age of 37.