Abstract

The thesis of this paper is that the only fully adequate way to describe the granularity of photographic materials is by means of a film noise spectrum. The film noise spectrum bears the same relation to granularity that the power spectrum (of electrical circuit theory) bears to electrical noise. The film noise spectrum includes all of the information in the previous granularity measures and readily interrelates them. It goes beyond the previous measures in that it leads to the solution of many of the signal-to-noise problems that arise in connection with the detection of target images on photographic materials.

The film noise spectrum is defined and discussed in Parts 2 and 3. Its relation to the older methods of description involving granularity coefficients, both ordinary and syzygetic, is the subject of Part 4. The superiority of the new method is explained in detail in Part 5. Part 6 employs the film noise spectrum to derive the relation between ordinary granularity and syzygetic granularity. Part 7 discusses photoelectric scanning of the film and derives general expressions for the signal and for the noise. These expressions are used in Parts 8 and 9 to derive a particularly convenient method for the measurement of the film noise spectrum, and to solve the general problem of maximizing the signal-to-noise ratio in the detection of target images. Part 10 discusses the film noise spectrum of Super-XX film.

© 1955 Optical Society of America

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