The extensive use of charge-coupled devices (CCDs) in astronomical imaging and spectroscopic applications has resulted in techniques being developed to correct for sensitivity variations attributable to the focal plane array detector. One normally overlooked effect is that these sensitivity variations also include intrapixel spatial effects that can influence measurements made with CCDs in certain circumstances. We demonstrate the influence of CCD pixel response nonuniformity on photometric measurements. An investigation is presented of how the relation between pixel size and the image size affects the photometric accuracy. Results are presented for a front-illuminated CCD array using an experimentally measured pixel sensitivity functions. © 2001 Society of Photo-Optical Instrumentation Engineers.