Supplementary Fig. 1.

Comparison of the average number of localisations per frame at different chamber pressures. Graph showing the average number of localisations per frame at atmosphere, 200 Pa, and 10⁻³ Pa across each 30,000 image sequence from consecutive serial sections (200 Pa data shown in Fig. 4; cropped areas shown in Fig. 5). The first 500 frames were excluded from analysis as the EMCCD was close to saturation and FP blinking was difficult to observe (indicated by vertical line).