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With appropriate weighting schemes applied to the interrogation areas, the image deformation PIV processing technique can be stabilized effectively even for a high percentage of interrogation area overlap. The potential of this technique to improve the spatial resolution of the PIV image processing is substantially limited by ambiguities of local deformations, leading to biased velocity estimates. Even if the remaining bias decreases with an increasing amount of locally available information (particle density and distribution), it is still present. This holds even if low-pass filters are applied, which can damp the fluctuations, but cannot avoid the tendency towards biased estimates. This also holds for the image deformation technique without interrogation area weighting. This ambiguity and the resulting bias vanish immediately, if the mean displacement of the interrogation areas during the deformation process is corrected towards the estimated velocity value. Unfortunately, this correction hobbles the degree of freedom of the deformation and, finally, limits the achievable spatial resolution to that of classical PIV. In summary, the results of this investigation, the only useful option to substantially improve the spatial resolution of the PIV process is to reduce the size of the interrogation areas. This requires an appropriate particle density to ensure an acceptable probability of outliers and hence, a carefully prepared experiment. The image processing itself cannot improve the spatial resolution. Even if an improvement of the spatial resolution would be possible for given PIV images, this would not be useful: In PIV image processing, the derivation of mean displacements averaged over the interrogation areas is a feature to improve the robustness and the accuracy in comparison to the tracking of individual particles. The size of the interrogation areas is chosen such that enough information (number of particle images) is available inside the interrogation areas to ensure an acceptably small probability of outliers. If the spatial resolution of the PIV processing is increased, the advantage is lost. It is not sufficient to resolve all flow structures at the new resolution with the same robustness and accuracy as before, since the available information is unchanged. This has the same effect as smaller interrogation area sizes, and thus there is no remaining advantage of the image deformation technique compared to the window shift and deformation.