  We present an event-by-event study of cosmic ray (CR) composition with the
reflected Cherenkov light method. The fraction of CR light component above 5
PeV was reconstructed using the 2013 run data of the SPHERE experiment which
observed optical Vavilov-Cherenkov radiation of extensive air showers,
reflected from snow surface of Lake Baikal. Additionally, we discuss a
possibility to improve the elemental groups separability by means of
multidimensional criteria.
