Design and Application of Precise Electronic Gauge for Dimensional Changes in Films

Paper presented at a Symposium on “Photographic Materials and Processes in the Printing Industry”, organized by the Scientific and Technical Group on 4–6 December 1963, in London.

Abstract

A standard type of electronic sensing element has been assembled into a comparator type gauging assembly which permits differential length measurement of photographic films and film bose with a high degree of reproducibility. Repeat measurements on strips nominally 9 5 in. long show a standard deviation of 0 00006 in. (60 microinches). This is at least an order of magnitude more precise than limits set in ASA standards for pin gauges or optical comparators as used in this field of measurement. In the assembly described, 900 measurements per 8 hour day can be made to the precision indicated with nontechnically trained operators. The higher precision permitted detection of effects difficult to measure quantitatively with existing gauges. Contrary to general belief, coatings contribute significantly to thermal coefficients of photographic films. Thermal expansion coefficients were generally constant but humidity coefficients were often variable with change of ambient conditions. Oriented and crystalline polyethylene terephthalate showed significantly less hysteresis and permanent shrinkage with humidity change than other film bases. Increasing the hydrophobic character of the binder yielded consistently lower dimensional changes.

Notes

Paper presented at a Symposium on “Photographic Materials and Processes in the Printing Industry”, organized by the Scientific and Technical Group on 4–6 December 1963, in London.