: Minimal fluorescence (arbitrary units). Fluorescence level of dark-adapted sample when all reaction centers of the photosystem II are open.
:  Maximal fluorescence (arbitrary units). Fluorescence level of dark-adapted sample when a high intensity pulse has been applied. All reaction centers of the photosystem II are closed.
: Minimal fluorescence (arbitrary units). Fluorescence level of light-adapted sample when all reaction centers of the photosystem II are open; it is lowered with respect to  by non-photochemical quenching.
: Maximal fluorescence (arbitrary units). Fluorescence level of light-adapted sample when a high intensity pulse has been applied. All reaction centers of the photosystem II are closed.
:  Steady-state terminal fluorescence (arbitrary units). A steady-state fluorescence level decreased (= quenched) by photochemical and non-photochemical processes.
:  Half rise time from  to .