We examine two issues that arise in connection with the description of dislocations in metals. First, the experiments of Mills and Stadelmann on Lomer dislocations in Al are considered in light of atomistic simulations of their core structures. It is shown that the results of such a microscopic analysis are consistent with those obtained earlier on the basis of image simulation. Secondly, we examine these Lomer dislocations using the recently developed technique of Computational Fourier Transform Moirè (CFTM) analysis. This technique allows for a determination of the strain fields near a defect directly from a high-resolution image without the necessity of obtaining a trial structure for the defect, complementing traditional approaches to the interpretation of high-resolution data.