We have compared simple stellar populations ( SSPs ) generated with different population synthesis tools : BC03 , Vazdekis and Pégase.HR and different stellar libraries : ELODIE3.1 , SteLib and MILES .
We find that BC03/SteLib SSPs are biased toward solar metallicity , however Pégase.HR/ELODIE3.1 and Vazdekis/MILES are extremely consistent .
The extensive coverage of the space of atmospheric parameters in the large stellar libraries allows precise synthesis for a large range of ages ( 0.1 .. 10 Gyr ) and metallicities ( -2 .. +0.4 dex ) limited by the quality of the determination of stellar parameters ( temperature scale of the giants ) .