The resolution limit of seismic data is a complex issue that involves not only wavelet frequency, phase characters, and data quality (S/N), but also criteria on how to measure resolvability. In his classic 1973 paper “How thin is a thin bed?,” Widess discussed the effect of bed thickness on re-flection character and timing using a symmetrical wavelet and suggested that λ/8 be the resolution limit, or the minimum distance at which a composite waveform stabilized as the derivative of the waveform from an individual reflection. However, this definition has more theoretical than practical impact because of the difficulties in judging waveform stabilization. A more workable and widely accepted definition of resolution limit corresponds to Rayleigh's criterion of peak-to-trough separation at λ/4 (Kallweit and Wood, 1982). This point is also a “tuning point,” at which composite amplitude reaches a maximum if an opposite-polarity (at top and bottom) thin bed is involved.