Influence of first developer solvent levels on the information storage capacity of negative and reversal images

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Title: Influence of first developer solvent levels on the information storage capacity of negative and reversal images
Author: Harrison, Wendy R.
Abstract: Silver halide solvents are commonly used in the first developer of a reversal process to obtain brighter highlights and a higher effective speed. An investigation was carried out to determine the effect of a low and high level of solvent on the sensitometric char acteristics as well as the covering power, granularity, modulation transfer function (MTF) and the information storage capacity of Plus-X reversal film 7276. The investigation was designed such that the only variable in the systems studied was the first developer. D-67, i.e., D-19 containing two grams liter^-1 of potassium thiocyanate, was chosen as the high solvent first developer. D-19 with twenty-five grams liter^-1 of sodium sulfite, designated D19-25 in this investigation, was the low solvent first developer. Four systems were studied: 1) negative images developed in a low solvent developer (D19-25) 2) positive images developed in D-19 using a low solvent first developer (D19-25) 3) negative images developed in a high solvent developer (D-6 7) 4) positive images developed in D-19 using a high solvent first developer (D-67) The information storage capacity for each system was calculated from the signal to noise ratio across the spatial frequency range of zero cycles mm^-1 to twenty-five cycles mm^-1. The signal to noise ratio was determined from the gamma value of the D-log H curves, the MTF and the Wiener spectrum ordinate value derived from the granularity. Comparisons between the systems were made for each parameter as well as the information storage capacity. The comparisons were made two different ways: 1) at equal densities and 2) at equal exposures. No significant differences attributable to the solvent were found in the granularity, MTF and the information storage capacity when the ccmparisons were made at density levels of 0.50, 1.00 and 1.50 above base plus fog. Differences were seen in the covering power of each system. Slower speed and dark highlights, as evidenced in the positive D-log H curves, were obtained using D19-25 as the first developer. In creasing the exposure to compensate for the lower speed would not correct the dim highlights. This indicated that perhaps a more viable comparison could be made at equal exposure levels. Differences were observed in the covering power, granularity and information storage capacity when the comparisons were made at equal exposure levels. The covering power did not appear to influence the information storage capacity results since the trends were not the same. The covering power of the D-67 negative system was lower than the D19-25 negative system due to solution-physical development effects. The covering power of the positive systems were not different. The covering power values obtained for the positive systems were about forty- five percent higher than the covering power values. The granularity affected the information storage capacity re sults the most. As the granularity increased across the exposure range the amount of information detected decreased. Larger dif ferences were observed between the positive systems than the negative systems . Positive images developed in D-67 showed cleaner highlights, i.e., a lower D_min. level on the D-log H curve, a higher effective speed, about a ten percent decrease in granularity and an increase of about eighteen percent in the information storage capacity. Processing in a high solvent first developer provided a distinct advantage over development in a low solvent developer in terms of the parameters investigated in this study.
Record URI: http://hdl.handle.net/1850/8305
Date: 1980-06

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