The first part of the third paragraph on p. 25466 should read: A further challenge in MFI is to detect the small fluctuations in the fluorescence at the magnetic null, above the larger unmodulated fluorescence from the remainder of the sample. In our experiment, the maximum AC component of the PMT voltage is V _AC = 100 μV, while the DC background is V _DC = 500 mV. To achieve a shot noise-limited SNR of 10, one must acquire at least n_phot = 100(V _DC/V _AC)² fluorescence photons at each pixel. This requirement can lead to unreasonably long image acquisition times. The background increases as V DC∝ N pix, where N pix is the number of pixels, while the maximum AC signal is independent of N pix. The number of photons required per pixel increases as N pix2, and the number of photons per image increases as N pix3. The rate of photon collection is proportional to N pix _, so the acquisition time per image increases as N pix2. Thus shot noise ultimately limits the number of pixels in an MFI image.

The rest of the paragraph remains the same as in the original paper.