Given an arbitrarily weak notion of left-f -porosity and an arbitrarily strong notion of right-g-porosity, we construct an example of closed subset of R which is not σ-left-f -porous and is right-g-porous. We also briefly summarize the relations between three different definitions of porosity controlled by a function; we then observe that our construction gives the example for any combination of these definitions of left-porosity and right-porosity. (C) 201