1. In the method of predicting the printing ink consumption of an off-set image, which method includes the steps of photoelectrically scanning the screened image from which the off-set image is to be produced along a linear scanning path, periodically sampling the resulting electrical signal, utilizing the signal samples to produce signal values representing the corresponding ink consumption requirements, and totaling and displaying the so-produced values, the improvement which comprises analyzing the screened image to determine the scanning and sampling rates which will produce samples reliably corresponding to the density of the image dots, and performing the scanning and sampling at the rates so determined, the analyzing comprising overlaying the screened image consecutively with glass screens having different line numbers, pivoting each screen back and forth to create moire patterns through interaction between the screen and the image, and determining the least conspicuous moire pattern so produced.