Particle size distributions obtained from a thin section are usually a
skewed version of the true distribution. A previous method for determining
the parent distribution was questionable because negative particle
frequencies could be obtained. Here, we describe a method of determining
parent distributions of spherical particles using a model with adjustable
parameters. Our calculated distributions are somewhat broader than the
distributions obtained with previous methods, but the average particle
sizes are nearly identical. The newly developed model is applicable to any
type of transmission microscopy.