[en] We propose to measure pion electroproduction off ¹H, ², ¹²C, ⁶⁴Cu, and ¹⁹⁷Au, and extract the pion transparency through the nuclear medium between Q² = 1 and 5 (GeV/c)². The pion transparency is predicted to be a signature of the onset of nuclear filtering and/or Color Transparency. Recent experiments have reported evidence for Color Transparency effects at Q² approx 10 (GeV/c)². The occurrence of nuclear filtering could potentially explain the apparent discrepancy between (proton) nuclear transparencies found in quasielastic A(e,e'p) and A(p,2p) experiments. The occurrence of these effects is an effective signature of the approach to the factorization regime in meson electroproduction experiments, necessary for the access to Generalized Parton Distributions. Measurable effects of approx. 40% are predicted for this region of Q². The proposed experiment seeks to measure the pion transparency with 5-10% uncertainties, dominated by systematics, up to Q² = 5 (GeV/c)²