An imaging system for electro-optically reading a symbol located within a range of working distances from the system, the symbol having a plurality of optical characteristics that vary with working distance, comprising: a) a solid-state imager having an array of image sensors for capturing return light from the symbol over a field of view, and for generating an electrical signal indicative of the captured return light; b) a controller operative for decoding the electrical signal into data indicative of the symbol, and for determining that the symbol has been successfully decoded; and c) a memory for storing a known set of values of the plurality of optical characteristics of the symbol when the symbol lies in a restricted zone within the range of working distances, and d) the controller being further operative, after the symbol has been successfully decoded, for processing the plurality of optical characteristics of the decoded symbol, and for determining that the decoded symbol has been successfully read within the restricted zone when each processed optical characteristic lies within the known set of values stored by the memory; wherein e) the symbol has elements of different light reflectivity, and of different width dimensions, along a scan direction; and wherein the controller is operative, in processing one of the optical characteristics as a symbol element size characteristic; and characterized in that f) the controller is operative, in processing another of the optical characteristics as a contrast characteristic, for estimating a contrast ratio of a first difference in brightness between symbol elements having the narrowest width dimension divided by a second difference in brightness between symbol elements having the widest width dimension. a) a solid-state imager having an array of image sensors for capturing return light from the symbol over a field of view, and for generating an electrical signal indicative of the captured return light; b) a controller operative for decoding the electrical signal into data indicative of the symbol, and for determining that the symbol has been successfully decoded; and c) a memory for storing a known set of values of the plurality of optical characteristics of the symbol when the symbol lies in a restricted zone within the range of working distances, and d) the controller being further operative, after the symbol has been successfully decoded, for processing the plurality of optical characteristics of the decoded symbol, and for determining that the decoded symbol has been successfully read within the restricted zone when each processed optical characteristic lies within the known set of values stored by the memory; wherein e) the symbol has elements of different light reflectivity, and of different width dimensions, along a scan direction; and wherein the controller is operative, in processing one of the optical characteristics as a symbol element size characteristic; and characterized in that f) the controller is operative, in processing another of the optical characteristics as a contrast characteristic, for estimating a contrast ratio of a first difference in brightness between symbol elements having the narrowest width dimension divided by a second difference in brightness between symbol elements having the widest width dimension.