It is a myth that more pixels alone result in better images. The marketing of camera phones in particular has focused on
their pixel numbers. However, their performance varies considerably according to the conditions of image capture.
Camera phones are often used in low-light situations where the lack of a flash and limited exposure time will produce
underexposed, noisy and blurred images. Camera utilization can be quantitatively described by photospace distributions,
a statistical description of the frequency of pictures taken at varying light levels and camera-subject distances. If the
photospace distribution is known, the user-experienced distribution of quality can be determined either directly by direct
measurement of subjective quality, or by photospace-weighting of objective attributes.
The population of a photospace distribution requires examining large numbers of images taken under typical camera
phone usage conditions. ImagePhi was developed as a user-friendly software tool to interactively estimate the primary
photospace variables, subject illumination and subject distance, from individual images. Additionally, subjective
evaluations of image quality and failure modes for low quality images can be entered into ImagePhi.
ImagePhi has been applied to sets of images taken by typical users with a selection of popular camera phones varying in
resolution. The estimated photospace distribution of camera phone usage has been correlated with the distributions of
failure modes. The subjective and objective data show that photospace conditions have a much bigger impact on image
quality of a camera phone than the pixel count of its imager. The 'megapixel myth' is thus seen to be less a myth than an
ill framed conditional assertion, whose conditions are to a large extent specified by the camera's operational state in