An imaging system for electro-optically reading a symbol located within a range of working distances from the system, utilizes a solid-state imager for capturing return light from the symbol and for generating an electrical signal indicative of the captured return light, and a controller for decoding the electrical signal into data indicative of the symbol A memory stores a known set of values for a plurality of optical characteristics of the symbol, such as size and contrast characteristics of the symbol when the symbol lies in a restricted zone within the range of working distances. The controller is operative, after the symbol has been successfully decoded, for processing the size and contrast characteristics of the decoded symbol, and for determining that the decoded symbol has been successfully read within the restricted zone when each size and contrast characteristic lies within the known set of values stored by the memory.