Detailed analysis of the vibronic structure in the electronic absorption spectrum of Cs2NaYbF6 at temperatures between 10 and 300 K enables the crystal field energy level diagram of Yb3+ in this cubic host to be deduced. Ultraviolet and visible laser excitation of Cs2NaYbF6, Cs2NaY0.9Yb0.1F6, and Cs2NaHo0.99Yb0.01F6 give spectral features mainly due to Yb3+ being situated at a range of defect sites. The 4f(13) crystal field analyses of octahedral YbX63- (X = F, Cl, Br) systems show the expected trends in parameter values, but the energy level fits are poor. Inclusion of the interaction with the charge-transfer configuration 4f(14)np(5) provides an exact fitting of energy levels for YbX63-, and a smooth variation of ff and fp crystal field parameters for Cs(2)NaLnCl(6) (Ln = Er, Tm, Yb) is observed.