Underwater imaging without color distortions requires RAW capture

Abstract: Consumer cameras are ubiquitous in aquatic sciences because they are affordable and easy to use, generating vast collections of underwater imagery for ecosystem surveys, monitoring, mapping, and animal behavior studies. Yet when color is the variable of interest, such as in coral-bleaching research, most of these images cannot be used quantitatively if captured in JPEG format. The limitation is not due to JPEG compression itself, but to the in-camera processing that precedes it: as cameras produce these images, built-in algorithms modify colors and contrast not to ensure color accuracy but to produce visually pleasing pictures. These irreversible in-camera operations break the linear relationship between pixel values and scene radiance, making colors impossible to standardize, reproduce, or compare across cameras, locations, or time. This essay explains the scientific costs of this practice and offers pragmatic guidance to prevent irreversible data loss, beginning with the capture and archiving of minimally processed RAW images.