Photo 51: what Franklin, Crick and Watson saw

The B-DNA preset, at its default settings, reconstructs the pattern in Franklin's photograph. The same image was read two different ways — with careful circumspection by Franklin, and at a glance by Watson — use the viewpoint toggle above the pattern to see why.

Radius (r)1.00 nm

DNA

TMV

Pitch (P)3.40 nm

DNA

TMV

Absolute scale1.00×

DNA/TMV

both 1×

Phase difference (Δφ)135°

Viewpoint

View zoom (K) — effective camera length1.00×

more layer linesfiner radial detail

The maths, with your numbers in it

Hover the pattern to inspect a point.

Each row is one layer line, from J_n(2πrρ) at the effective radius, positioned at height ∝ n / effective pitch. Row shape is normalised for visibility; with 2 strands, each row's overall brightness is additionally scaled by cos²(nΔφ/2) — watch a whole row fade as Δφ sweeps through its extinguishing angle.