  This paper reports the results obtained on the photometric redshifts
measurement and accuracy, and cluster tomography in the ESO Distant Cluster
Survey (EDisCS) fields. Photometric redshifts were computed using two
independent codes (Hyperz and G. Rudnick's code). The accuracy of photometric
redshifts was assessed by comparing our estimates with the spectroscopic
redshifts of ~1400 galaxies in the 0.3<z<1.0 domain. The accuracy for galaxies
fainter than the spectroscopic control sample was estimated using a degraded
version of the photometric catalog for the spectroscopic sample. The accuracy
of photometric redshifts is typically sigma(Delta z/(1+z)) ~ 0.05+/-0.01,
depending on the field, the filter set, and the spectral type of the galaxies.
The quality of the photometric redshifts degrades by a factor of two in
sigma(Delta z/(1+z)) between the brightest (I~22) and the faintest (I~24-24.5)
galaxies in the EDisCS sample. The photometric determination of cluster
redshifts in the EDisCS fields using a simple algorithm based on photoz is in
excellent agreement with the spectroscopic values (delta(z) ~0.03-0.04 in the
high-z sample and ~0.05 in the low-z sample). We also developed a method that
uses both photz codes jointly to reject interlopers at magnitudes fainter than
the spectroscopic limit. When applied to the spectroscopic sample, this method
rejects ~50-90% of all spectroscopically confirmed non-members, while retaining
at least 90% of all confirmed members. Photometric redshifts are found to be
particularly useful for the identification and study of clusters of galaxies in
large surveys. They enable efficient and complete pre-selection of cluster
members for spectroscopy, allow accurate determinations of the cluster
redshifts, and provide a means of determining cluster membership. (Abridged)
