Studies on resolving power of photographic lens under varing conditions of test chart are given. Experiments show that difference of chart contrast affects the position of the best resolution, and this is explained by the combined response function of lens and emulsion. Further consideration shows that suitable contrast of test chart for image evaluation is about 0.2 density unit, because the best focus of the chart of this contrast coincides with maxima of information volume which is considered as the measure of performance of the optical system.
Further considerations on photographic lens performance with “information volume” defined in the author's previous paper1), is described. Information volume in two dimentional domain is analogous to Strehl's “Definitionshel-ligkeit” and has characteristics of absolute measure of lens performance. There is phase shift on response function when response has odd component. This phase shift means optical distortion of higher order, and the author defined it as “phasic distortion” The principle and methods of experiments with emulsion and model of emulsion are given.
The resolving power of photographic lenses is measured by photographing a test chart, and its value depends on ΔD, the least perceptible density discrimination of the photographic negative. ΔD is influenced not only by acuity of the human eye, but also by the newly defined quantity Ga, the apparent graininess of the photographic negative. Relation between ΔD and Ga is found experimentally, and the result enabled the author to deny the contradiction in the previous paper concerning the absolute representation of resolving power.
Many investigations have been made in the past on quenching of photoconductivity of CdS crystals by infrared irradiation. But the existence of quenching outside infrared region has not been explored. It is found that the irradiation of the wave-length shorter than that gives the maximum photoconductive efficiency (about 5200A) causes the quenching effect as well as the excitation effect. Further, the photocurrent produced by superposing several excitations is found not additive. This fact should be noted when CdS crystals are used as a detector of radiations. Experimental results on quenching by shorter wave irradiation with accompanying interesting phenomena are described.
An apparatus has been devised with which scattered flux of light from surface of paper is decomposed into specular and diffuse components. The incident light is plane polarized and the scattered flux is passed through a rotating polaroid sector, a polaroid analyzer and directed to a photomultiplier generating A. C. signals which are amplified, rectified and indicated. The indicator is set to zero reading by turning the analyzer to an angle A which, when the electric vector of the incident polarized light is perpendicular to the plane of incidence, is given by D/M=sin 2A-l, where D and M are specular and diffuse components respectively. The polaroid sector and analyzer are then removed and goniophotometric measurement enables the resolution of the scattered light into specular and diffuse components by the above equation. The following results are obtained. 1. A fairly satisfactory conclusion is arrived at by assuming that the specular component remains polarized with unchanged plane of polarization and that the diffuse component is completely depolarized. 2. The diffuse component from coated paper follows Lambert's law but that from uncoated paper does not. 3. The specular component does not follow Fresnel's formula due probably to the fact that the reflection from paper is not explained by geometrical optics alone which makes Barkas' analysis not applicable to paper in general. 4. In some cases, the angle of maximum intensity of reflection is not equal to the angle of incidence which is explainable if the diffuse component and both relative area and reflection coefficient of mirror facets are considered.
New distinctness-of-image gloss meter has been constructed. In this experiment, the distinctness-of-image on samples are obtained by measuring the ratio of the intensity of specularly reflected light to the-intensity of diffusely reflected light, the angle between them being about 1°. The distinctness-of-image gloss of high gloss paints which have almost the same values of the specular gloss is investigated. The ranking of these samples determined by the obtained results with this new method shows fair agreement with the visual ranking by 15 observers.
The sensitivities of the first order sensitive colors are measured with parallel and crossed Nicols. The results are as follows. (1) The sensitivity with parallel Nicols is about 1.5 times higher than that with crossed Nicols, showing good agreement with calculated values, as predicted by H. Kubota. (2) Retardations, at which the sensitive colors are given, are 293.7 mμ in parallel Nicols and 584.4 mμ in crossed Nicols, deviating 13.9 mμ and 24.8 mμ to blue side respectively from the calculated values. (3) The sensitivities of the measurement of retardation by sensitive colors are about 4.2Å with parallel Nicols and about 6.7Å with crossed Nicols.