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746 Transactions of S.M.P.E., Vol XI, No. 32, 1927
in density from one tablet step to the next. If the printer test exposures have been developed as described, the density difference between any two of them will be equal to the density difference between the corresponding tablet steps. (This may not hold if the range of exposures given by the printer is much greater than usual or if the range is extremely high or low.)
5. Comparison of each Tablet Step with the Corresponding Printer Step and Final Adjustment of the Tablet
The final procedure is to make such alterations in the trial tablet as are found necessary to bring about perfect agreement with the printer. In matching the printer and sensitometer at any particular step, it is best to make actual prints from a uniform, good quality negative which is known to be suitable for printing at that particular step. Variations in density from frame to frame of the negative will cause no trouble if the precaution is taken to compare prints from the same frame as printed on the sensitometer and printer. This is facilitated by putting characteristic scratch marks in one corner of each frame. Only about two feet of negative are required for this purpose. To be satisfactory, these comparison strips must be developed not only together but to a sufficient degree of contrast to make a print of good quality. In this manner, one step at a time is brought into agreement with the printer with the use in every case of a proper negative.
The intensity of illumination of the tablet should permit an exposure of at least six seconds for manual operation and should be adjusted so that this is the case when the printer and sensitometer agree.
For a sensitometer in which the exposure is timed by a mechanical means, the time should be equal as nearly as possible to the exposure time given by the printer. If the timing involves turning on and off the current of the lamp, this time should be sufficiently long so that the time required for the lamp to reach full brilliance is only a small fraction of the total time of exposure.
6. Testing the Sensitometer
From time to time it is. necessary to test the sensitometer to
find out if it is in good agreement with the printer. Since changing
the time of exposure is, in the case of most sensitometers, exceedingly
impractical and always undesirable, it is necessary to adjust the