We renormalize, using suitable lenses, small domains of a singular holomorphic foliation of $C^2$ where the curvature is concentrated. At a proper scale, the leaves are almost translates of a graph that we will call "profile". When the leaves of the foliations are levels $f = \lambda$ where $f$ is a polynomial in 2 variables, this graph is polynomial. Finally we will indicate how our methods may be adapted to study levels of polynomials and 1-forms in $C^3$