# Photograph 49 Explains Franklin's DNA Work

> Rosalind Franklin used Photograph 49 to calculate DNA structure before creating Photograph 51.
- Title: Photograph 49 Explains Franklin's DNA Work · SpringerLink
- Summary: Rosalind Franklin used Photograph 49 to calculate DNA structure before creating Photograph 51. Rosalind Franklin reused DNA sample for Photograph 51 after…
- Keywords: rosalind franklin, photograph 49, photograph 51, dna helix, x-ray crystallography, james watson, technology, startups, Photograph, Explains, Franklin's, DNA
- Source: SpringerLink — https://link.springer.com/article/10.1007/s10739-026-09866-7
- Published: 2026-10-05T00:00:00+00:00
- Read time: 1 min
- Topics: rosalind franklin, photograph 49, photograph 51, dna helix, x-ray crystallography, james watson, technology, startups
## Photograph 49
This image helped Rosalind Franklin calculate DNA's B form helix parameters.

> We show that she had in fact already made those calculations, on her earlier Photograph 49
## Photograph 51
Franklin reused the same DNA sample for a better-centered diffraction image.

> she reused the same DNA sample for Photograph 51 to create a better-centered but otherwise identical diffraction image
## Why Photograph 51 Was Created
Franklin took Photograph 51 because she knew key DNA helix parameters could be calculated from it.

> she decided to take Photograph 51 precisely because she knew that key parameters of DNA’s B form helix could be calculated
## The Misunderstanding
Colleagues described Photograph 51 as nature speaking for itself, ignoring Franklin's calculations.

> colleagues and later commentators did not merely overlook Franklin’s original reason for creating Photograph 51
## The Correction
Franklin had already performed the calculations on Photograph 49 before creating Photograph 51.

> We refute the infamous claim that Franklin failed to see the picture’s potential significance for interpreting the helical structure of DNA
## Key takeaway

Rosalind Franklin reused DNA sample for Photograph 51 after calculating DNA helix parameters from earlier Photograph 49.