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Surface brightness fluctuation (SBF) is a phenomenon evident when observing galaxies: the more distant the galaxy, the smoother its observed surface brightness. This is not about fluctuations (changes) over time, but about fluctuations (unevenness) across the surface, such as the extra brightness where there happen to be bright stars. The smoothing is due to the telescope and instrument's resolution. The relation of "amount of fluctuations" to distance is imperfect, yet sufficiently consistent to give a distance estimate for elliptical galaxies (the surface brightness fluctuations method). The estimate is improved by taking other characteristics of the galaxy into account.