This paper presents an acoustic study on the phonetic properties of French schwa based on the analysis of a large corpus of radio broadcasted news. In order to address the question of whether the optional status of schwa correlates with a specific phonetic nature, optional French schwa is compared to its neighboring full front rounded vowels /2/ and /9/, and to obligatory schwas. While optional schwas overlap with the acoustical space of its neighbors (being closer to /2/), it differs from both /2/ and /9/ in terms of aperture, degree of rounding, duration and variability of F2. Optional schwas differ from obligatory schwas by a greater aperture.