Table 2.

Relationship of success rate to the number of particle images.^*

Number of Particle Images	Success Rate (%)	Iteration at Convergence§
500	20	----
1,000	20	----
3,000	40	80 (±23)
10,000	40	58 (±15)
76,000	90	57 (±23)

^*Ribosome data set with 10 independent tests per entry. Angular step-size: initial 20°, each successive iteration changed the step-size by −0.19°. Average defocus, 2.9 μm underfocus.

^§Iteration at which the correct structure appeared (average ± standard deviation), made by visual assessment of maps at iterations 10, 20, 30, …, 100. The average number of iterations required for convergence to a suitable model declined substantially from 3,000 to 10,000 particle images, but declined insignificantly between 10,000 and 76,000 particles. Only a representative number of cases were assessed.