The present invention is directed to a method and apparatus of objectively testing the low contrast performance of an imaging system. Images of a uniform phantom and images of a low contrast detectability phantom are reconstructed. Thereafter, a group of pixels from an image of the uniform phantom are removed and replaced with a group of pixels from an image of the LCD phantom. A user or test observer is then prompted to identify which quadrant of the first phantom image contains a group of pixels from the LCD phantom. An accuracy of a user response is then determined and conveyed to the user. The present invention is applicable with a number of imaging modalities including computer tomography, magnetic resonance imaging, PET, ultrasound, and the like.