The Rayleigh Principle states that the minimum separation between two reflectors that allows them to be visually separated is the separation where the wavelet maxima from the two superimposed reflections combine into one maximum. This happens around Δtres = λb/8, where λb is the predominant wavelength of the wavelet within the thin layer. Using a simple thin-layer parameterization Widess (1973) demonstrated that thin layers with thickness less that around λb/8 cannot be resolved from seismic data independent of the noise level. This has results since been widely adopted as a commonly accepted lower vertical resolution of reflection seismic data. In the following we will revisit think layer model and demonstrate that there is in practice no limit to the vertical resolution using the parameterization of Widess (1973), and that the vertical resolution is limited by the noise in the data. In general, we discuss that the resolution of reflection seismic data is controlled by the noise level and the a priori information available