  In low $\gamma$ regimes the inevitable induced energy spread in combination
with longitudinal dispersion during the drift through a transverse deflecting
structure (TDS) can alter the phase space of the particle bunch to be
characterized. The consequential bunch lengthening can render measuring
ultra-short bunches impossible, even for high available streaking powers and
hence theoretical resolution. In this work the resulting effective resolution
of a TDS is estimated analytically and the optimal streaking voltage is
determined. The findings are subsequently benchmarked using matrix-based
particle tracking. Furthermore, additional transverse, as well as other
resolution limiting effects of a realistic streaking setup are discussed. A
potential mitigation scheme using an additional downstream focusing element is
evaluated.
