The Calculation of Characteristic Values of Photographic Materials by Using a Mathematical Model

In sensitometry,the characteristic values of sensitivity and contrast coefficient are generally,obtained from photographic characteristic curve graphically.Because of the low graphical accuracy,the determined values are quite inconsistent.Masao Inui and Syuji Kashiwa(Japan) have suggested a mathematical model which may be used to calculate numerically the photographic characteristic values.In this paper,the equations to calculate the sensitivity and contrast coefficient by the model are analysed and the procedure of calculation by adjustment is derived.Ten characteristic curves were calculated in the TQ-16 electronic computer and the obtained values were compared with the graphical ones(five persons).It was found that the discrepancies of sensitivity and contrast coefficient were within ±0.6 and ±0.06 respectively.The result was consistent with the experiment carried out by Masao Inui and Syuji Kashiwa.The adopted mathematical model is proved to be very practicable.