A review on the progress in photography in the year of 1962: about cameras, lenses and camera accesories, light sources, sensitive materials, theory of photographic sensitivity, processing, sensitometry, cinematography, scientific photography and color photography.

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The theoretical equation on variation of electric conductivity of ionic crystal with irradiation time was derived by assuming interaction of electron (or positive hole) and interstitial silver ion (or vacancy). This equation is non-linear equation containing five factors such as number of electro-conductive lattice defect (A), number of photon (C), and reaction rate constant (K₁, K₂, K₃). The equation can be solved by numerous integration, if initial condition was given. As example, the solution was shown. In the case where A, C, and K_i (i=1-3) are respectively 10¹⁴, 10¹⁶, and 10^-8. This theoretical results were agreed with the experimental results.

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The effect of concentration of lattice defects in ionic crystal upon photoconductivity was investigated by using theoretical equation on photoconductivity vs. irradiation time. The results showed that the decrease of photoconductive positive effect was decreased with the increase of the concentration. This tendency agreed well with the experimental results.

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The effect of intensity of light illuminated on ionic crystal upon photoconductivity of the ionic crystal was investigated by using the theoretical equation on photoconductivity vs. illuminating time.
The theoretical analysis was applied to such a crystal that is easy to show photoconductive negative effect because of its high concentration of lattice defects, and it was shown that the negative effect is weakened with the decrease of light intensity. This tendency was agreed with the experimental results.

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Experiments were performed to determine the recognition of three kinds of 16mm. black and white negative-films. At first, circle-square target was used, and only the contrast of the image was varied using an image of comparatively large size. Also, the negative image was purposely made vague by properly making it out-of-focus to make the sharpness of the optical system and the film negligible. When the recognition index of Barrow was measured by varying the negative density, developing time, and the gradation of the positive material, (1) the recognition index reached its maximum at a comparatively low negative density and with comparatively weak development, and (2) the effect of the gradation of the positive material was little, as Barrow reported. All these results are well explained by the change of graininess. The graininess is an important factor that affects the recognition.
In the second experiment, the size-contrast recognition was measured under the conditions of actual photographic procedures. The recognizable size of a square target was about 0.05-0.09mm. square, when the contrast was sufficiently high. When a camera lens, having a focal length several times that of a naked eye, is used-the size of the image on a film is several times that of the image size on the retina-it is almost equal to the recognition of a normal eye.

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