Figure 1.

(a) Correlation calculated from single structures that have continuous reciprocal-space intensity on a 2D detector, as has been previously used for single particles or amorphous materials. The angular correlation is calculated with respect to scattering magnitudes q₁ and q₂, and angle ψ, according to equation (1). (b) Correlation of Bragg peaks on a 2D detector. The intensities of every pair of points are multiplied and summed together according to their scattering magnitudes q₁ and q₂, and the angle ψ between them, according to equation (2). This illustration would apply to FXS-based crystallography experiments. (c) Correlation of Bragg peaks in 3D reciprocal space. Intensities are similarly multiplied and summed together according to equation (4). This method was used in this article for algorithm development because it is efficient to compute and it provides the ‘ground truth’ of correlation intensity.