Laser pulse shaping in picosecond time scale is widely applied in various laser with mater interactions. The pulses are generated by means of phase and amplitude modulation of femtosecond laser pulses using programmable spectral filters with complex transmission. Such filters are either spatial light modulators or acousto-optic dispersive delay lines. It is demonstrated that contrast and resolution in chirped laser pulse shaping follow the uncertainty principle and the optimal filter bandwidth equals to doubled spectral width of the laser radiation. The results are validated in experiment in a Ti:sapphire femtosecond laser system with a high-definition acousto-optic dispersive delay line.