Understanding the generation, transport and capture of charge carriers in semiconductors is of fundamental technological importance. Yet, conventional techniques average over many events, masking the nanoscale processes that critically influence performance. Here, we combine widefield optical microscopy with precision spectroscopy to examine the capture of photogenerated holes by negatively charged nitrogen vacancy (NV-) centers in diamond under cryogenic conditions. Simultaneous single-shot charge readout and electrometry over hundreds of individual NVs allows us to resolve the roles of ionized impurities, reveal the formation of space charge fields, and monitor the thermalization of hot photo-carriers during diffusion. We demonstrate the near-complete neutralization of coexisting-space charge via photo-carrier injection, drastically reducing spectral diffusion and increasing the effective NV- hole capture radii above 0.2 µm, a value approaching the Onsager limit. These results establish a new platform for resolving charge dynamics beyond ensemble averages, with direct relevance to nanoscale electronics and quantum devices.