Percentage numbers of spot identifications versus numbers of incident photons on the diffraction-limited spot. (A) Comparison between CCD, EMCCD, sCMOS and SPAD array cameras (with 70% photon detection efficiency). CCD camera had the worst performance with high readout noise, whereas the EMCCD camera with higher photon-detection efficiency (~90%) performed worse than expected owing to excess noise. (B) Comparison between performance of SPAD array cameras with EMCCD for different photon detection efficiencies. The SPAD array camera with a PDE of 90% performed better than EMCCD cameras. A fixed thresholding criterion was adopted for the simulations. The results and therefore the relative ranking of the cameras can vary depending on the type of criterion used for the identification of a spot.