  We study the photometric properties and content of the distant clusters of
galaxies Cl 1613+3104 (z = 0.415) and Cl 1600+4109 (z = 0.540). The former is a
rich, concentrated cluster which shows a strong evidence for segregation in
luminosity and color. Its population of galaxies separates into two different
kinds of objects: a red population compatible with the colors expected for E/S0
galaxies located preferentially in the central part of the cluster, and a
sparse blue population explained in part by the presence of normal S/Im
galaxies, which is much less concentrated. In the case of Cl 1600+4109, there
is a lack of E/S0 galaxies and the population is mainly made up of S/Im
galaxies, without any evidence of segregation in magnitude or in color. Both
clusters exhibit an important fraction of blue objects, increasing with
magnitude. This result is due in part to the presence of normal S/Im galaxies,
and also to extremely blue objects probably undergoing an episode of intense
star-formation.
