My aunt, Freda Collier, who has died aged 97, became well-known in the early 1950s as part of the core team of Maurice Wilkins, John Randall and Rosalind Franklin (plus Franklin's PhD student, Raymond Gosling) working at King's College London on the structure of DNA. Freda was Franklin's x-ray photographer and headed the photographic laboratory at King's that produced the famous "photo 51" seen by James Watson from Cambridge University. Watson immediately realised that the molecule revealed was a double helix.
As Watson described later in his book The Double Helix (1968): "The instant I saw the picture my mouth fell open and my pulse began to race." After the announcement by Watson and his colleague Francis Crick in 1953 that the structure of DNA had finally been cracked, Freda travelled extensively in the US explaining the x-ray diffraction techniques used by the King's College team.
She was born Freda Ticehurst in St Leonards-on-Sea, East Sussex, the youngest of seven surviving children – five girls and two boys. Her early years as a photographer were at the General Electric Company in Wembley, north London, where Randall had previously worked, and it was he who persuaded her to join the King's College team in 1950.
Her fiance had been killed during the second world war, but later she met and married the distinguished Church Army captain Frank Collier and settled in Folkestone. There were no children of the marriage, but she enjoyed the company of her many nieces and nephews, and later in life the triplets of Lynne and Paul Jones – a family who lived across the road – who became her surrogate children. Lynne cared for Freda in the years after Frank's death in 2010.
Freda was a devout Christian and shared fully in the church life of her husband, raising thousands of pounds for charities in different parts of the world. Her forte and passion was propagating plants and selling them at coffee mornings. Her enthusiasm for life was infectious, as was her laugh. Her energy was boundless, and even in her late 80s and partially blind, she and Frank would set off by train for their annual holiday in Lugano, Switzerland, changing trains in Paris laden with luggage (Frank hated flying).
My aunt was the closest confidante of Franklin, who died of ovarian cancer in 1958 before the Nobel prize in medicine was awarded to Crick, Watson and Wilkins in 1962 for unravelling the structure of DNA. It was a great regret to Freda that Franklin's contribution to the discovery was never fully recognised. The eminent physicist JD Bernal once described my aunt's photographs as "among the most beautiful x-ray photographs of any substance ever taken".
She is survived by four nephews and five nieces.