The major factors influencing the successful measurement of particle size from Particle Imaging Velocimetry (PIV) image data are described. Components of a standard PN system, a high resolution CCD camera and argon ion laser, are used to capture images of stationary particles. The image data are used to ascertain the limitations of estimating particle size. The effects of the Gaussian distributed intensity variation across the depth of the light sheet and the optical collection system's depth of field are investigated. These effects provide insight into designing a balanced illumination and collection optical system necessary to obtain constant particle size estimates, independent of their position within the light sheet. Using a 'balanced' optical set-up, monodisperse particle images are shown to be reproducible and predictable over a range of particle sizes and fields of view. Accuracy in the particle size estimates on the order of 9% are obtained consistently. It is also shown that size distributions in a mixture of polydisperse particles can be obtained with a maximum deviation of 10-20% from the true size distribution.