We present a stellar populations analysis of the first release of the CFHTLS ( Canada-France-Hawai Telescope Legacy Survey ) data .
A detailed comparison between the Besançon model of the Galaxy and the first data release of the CFHTLS-Deep survey is performed by implementing the MEGACAM photometric system in this model using stellar atmosphere model libraries .
The reliability of the theoretical libraries to reproduce the observed colours in the MEGACAM system is investigated .
The locations of various stellar species like subdwarfs , white dwarfs , late-type and brown dwarfs , binary systems are identified .
The contamination of the stellar sample by quasars and compact galaxies is quantified using spectroscopic data from the VIMOS-VLT Deep Survey ( VVDS ) as a function of i ^ { \prime } magnitude and r ^ { \prime } - i ^ { \prime } colour .
A comparison between simulated counts using the standard IMF at low masses show that the number of very low mass dwarfs may have been underestimated in previous studies .
These observations favour a power law IMF following d ( n ) / dm \propto m ^ { - \alpha } with \alpha = 2.5 for m < 0.25 M _ { \odot } or \alpha = 3.0 for m < 0.2 M _ { \odot } for single stars .
The resulting LF is in agreement with the local LF as measured from the 5 or 25 pc samples .
It is in strong disagreement with the Zheng et al ( 2001 ) LF measured from deep HST data .
We show that this discrepancy can be understood as an indication of a different IMF at low masses at early epochs of the Galaxy compared to the local thin disc IMF .