Accurate characterization of particle size and particle size distributions is mandatory in nanotechnology and a broad range of colloidal sciences. The size of colloidal particles can be determined using various techniques in direct and reciprocal space, including electron microscopy and static and dynamic light scattering. Differential dynamic microscopy was introduced recently and offers a new alternative. In this paper we present a systematic study of particle size determination using various techniques. We compare the results and highlight advantages and disadvantages. Unexpectedly we find that differential dynamic microscopy offers the unique possibility to determine the particle size in highly turbid samples.