Hummm ! Weellll !! The subtitle of my question could be :"Just call me dumbass" ! FWTempest you're damn right. In fact in the rendering tab, i've just see that in fact i've inverted all the values regarding precision of objects/lights, setting them to the max value, which in fact means... the lowest detail.... I think i need serious holidays :-) So thanx a lot for your help : so let's got back to render and to burning some CPUs... :-)