We present a detailed calculation of model atmospheres for DA white dwarfs .
Our atmosphere code solves the atmosphere structure in local thermodynamic equilibrium with a standard partial linearization technique , which takes into account the energy transfer by radiation and convection .
This code incorporates recent improved and extended data base of collision induced absorption by molecular hydrogen .
We analyse the thermodynamic structure and emergent flux of atmospheres in a range 2500 \leq T _ { eff } \leq 60000 K and 6.5 \leq \log g \leq 9.0 .
Bolometric correction and colour indices are provided for a subsample of the model grid .
Comparison of the colours is made with published observational material and results of other recent model calculations .

Motivated by the increasing interest on helium core white dwarfs , we analyse the photometric characteristics of these stars during their cooling , using evolutionary models recently available .
Effective temperatures , surface gravities , masses and ages have been determined for some helium core white dwarf candidates , and their possible binary nature is briefly discussed .