Figure 1. Sample motion and long integration time reduce spatial resolution.

(A) When imaged through an optical system, photons emitted by a point source hit the image plane at any given position with a probability related to the point spread function. (B) When the point source is in motion (with a velocity v) it produces a smeared point spread function whose extent Tv (with T the integration time) can exceed the extent of the point spread function resulting from diffraction alone. (C) In this simulation we consider ring-like structures that are moving with a uniform velocity from left to right. (D) As the integration time T increases, the equivalent point spread function becomes more elongated. (E) When the sample is bright, it appears blurred as the integration time increases. (F) Dim, moving samples require both short integration times to limit the spread of the point spread function, but also a sufficient photon count to yield satisfying signal to noise, thereby calling for a compromise between resolution and detection. (G) Single slice of a beating embryonic zebrafish heart imaged with a spinning disc confocal microscope at increasing frame-rates and decreasing integration times. Longer integration times result in images with motion blur artifacts but higher photon counts whereas high frame-rates have lower signal to noise ratio requiring, again, a compromise. Scale bar is 50 μm. [See also Supplementary movies (EPAPS)].