I carried out analytical experiments to study the eye-sight in relation to the illumination for the fog, using the fog-chamber which I designed. Results of my experiments are that:-
(1) The visual acuity through fog is weakened by the increas of the white area which encloses Landolt's rings.
(2) As the illuminating-angll upon the fog becomes larger, the visual acuity through fog becomes lower.
(3) When the fog is relatively faint and the useless light is covered completely, the visual acuity becomes better by the increase of the illumination. Other wise when the useless light is covered incompletely, the visual acuity does not become better by the increase of the illumination on the test type.
(4) The visual acuity through Loy becomes better by the application of the orrnge-coloured glass filter (matsuda's filter VO₃) in front of an eye.
The result of these experiments indicate that in order to maintain eye-sight through fog to prevent the light veil is the important matter concerning the illumination in the fog.

View full abstract