In connection with the parameters characterizing the phase noise in cw mode-locked lasers and under the employ of streak cameras operated by sinewave deflection, this paper discusses by a stochastic description the timing capabilities of the measuring system for two commonly used synchronization techniques. Especially, the power spectrum of the sweep signal versus the laser phase noise is examined in detail. The theoretical results are used to interpret experimental observations recorded by means of actively and passively mode-locked lasers. One of the interesting applications of synchroscan operations to metrology is the determination of short-term instabilities of the oscillator on a time scale near to the period.