A photographic method of changing the ratio of ordinate‐scale to abscissa‐scale
W. J. Peters, J. W. Green · Terrestrial Magnetism and Atmospheric Electricity · 1931
This method is proposed for the purpose of reproducing magnetograms or other continuous photographic records made at different observatories on the same scales as regards both time and value of magnetic or other recorded element with all the minutiae of detail. Two photographic exposures are made, one of the photographic record, the second of the resulting negative. In both exposures the sensitized paper is inclined at predetermined angles which depend upon the magnifications required of the abscissae and ordinates, respectively, and upon the condition that the respective scales be uniform throughout the final positive. Theoretically there is no limit to the choice of ratio desired between the scale of ordinate and the scale of abscissa. Practically the limit is fixed by the depth of focus available, and the smallest stop usable, or by the number of repetitions of the operation of two exposures. Experiments were made in which the final ordinates were made about three times as long as the original with respect to the abscissae in the one operation of two exposures.