Crystal Orientation Mapping (COM) of fine grained or deformed material is highly dependant upon the microscope performance, i.e. spot size and control of aberrations. In addition, the Electron Backscatter Diffraction (EBSD) camera sensitivity dictates the minimum probe current that can be used. Beyond the instrumental set-up, the condition of the sample is critical. Recent work has shown that the smallest grain size that can be measured is ultimately limited by strain present at the grain boundary. The "effective resolution" of EBSD information is approximately 6 nm using a Field Effect Gun Scanning Electron Microscope (FEG-SEM), and 30 nm using a Tungsten (W) filament SEM (W-SEM). However, when strain is present at the grain boundaries in the sample, the minimum grain size that can be determined is limited to similar to50 nm and 150 nm respectively. Deformed material is often an aggregate of smaller grains forming the interior of larger grains, with varying degrees of strain being residual within the structure and concentrated at grain boundaries. Thus high spatial resolution is critical to achieve continuous coverage of EBSD data. In the case of deformed material, the FEG-SEM achieves the best continuity of crystal orientation information across deformed areas. Therefore, the FEG-SEM offers a considerable advantage compared to the W-SEM under these circumstances.