Sine-Wave Response Techniques in Photographic Printing*

A single photographic emulsion serves as a linear device when analysis is made in terms of the exposure that the material receives. When sinusoidal patterns are printed, harmonics in terms of the transmittance of the negative are introduced in the print, but the odd and even harmonics tend to compensate each other so that the over-all error tends to be small even though the modulation of the sinusoidal pattern may be as large as 60% or 70%. The response function in terms of the exposure of the negative should therefore approximate the product of the sine-wave response functions of the two materials and should be little affected by processing conditions. Experimentally, these conclusions are found to hold very well when a contact print of good quality is made on positive film, even through as many as three successive printings. It is also found that such cascaded response functions can be used to predict the density distribution across an edge.