Energy resolution, like intrinsic spatial resolution, depends largely on statistical fluctuations in the number of light photons collected from a scintillation event (Chapter 10, Section B.7). Thus good light collection efficiency is a prerequisite for good energy resolution. As well, because the number of light photons released in a scintillation event increases almost linearly with γ-ray energy, E, (Fig. 10-11), energy resolution improves approximately in proportion to 1/ E (Fig. 10-13).