When the photographic emulsions were applied pressure before exposure, the surface and the shallow internal images were desensitized, but the deep internal image was sensitized.
When undigested photographic films containing the small quantity of sodium thiosulphate or ammonium aurous thiocyanate was incubated after the application of pressure, the surface image of pressed part of films was preferentially sensitized by following exposure.
However, the chemically sensitized emulsions digested to its maximum sensitivity was desensitized under the same conditions.
Also, the total latent image of non-sensitized emulsions incubated after the application of pressure was desensitized by following exposure.
It was shown that the sensitizing product was also formed at the crystal imperfections produced by pressure.
This result supported the Mitchell's theory that the sensitizing product was formed at the surface of the strained and imperfect regions of microcrystals.
The addition of thallous ions has been reported to decrease the desensitization produced by pressure.
This is explained by that silver halide grains containing thallous bromide are subjected to very slight deformation, because of its high hardness number.

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Examinations were made on the variation in the value of covering power and sizefrequency distribution of developed silver particles with changes in the amount of exposure and development, and on interrelationship, if any, between covering power and variation in size-frequency distribution of developed silver particles.
The sample used for this experiment was a Fuji positive film, exposed for 16 seconds and developed with FD-3 developer diluted with an equal volume of water. The mass of silver developed was determined by colorimetry and size-frequency distribution of the developed silver was calculated by taking an electron microscopic photograph of the developed silver particles and measuring their area. For the measurement of area of electron microscopic photograph of the developed silver particle, the area of silver particles in the photograph was cut out and weight of the cutting was measured.
The following results were thereby obtained.
1. In the toe region of the characteristic curve, increased density is due chiefly to the increase in the number of developed silver particles while in the shoulder region, increased density is due to the increase of both the number and size of developed silver particles.
2. The value of covering power does not change in the shoulder region of the characteristic curve. This is due to the fact that both the average size and effective density of developed silver particles have attained a constant value.
3. The dependency of the covering power of fog silver on exposure differs from that of image silver formed by exposure and development. It may be concluded that fog silver and image silver are of essentially different nature.

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