The Moving Picture World (1907)

3* THE MOVING PICTURE WORLD. All officers inspecting machines must file in this office a duplicate of permits to the operator, as well as the ma- chine number, maker's name and tag number. All rules pertaining to moving picture machines here- tofore promulgated are discontinued upon the issuance of the above rules. Approved: Joseph E. Shaw, Chief, Massachusetts District Police. Inspection Department, District Police, Chief's Office, State House, 190 . Permit is hereby granted , of > ../... to have charge of and operate any moving picture ma- chine that is approved, tagged and sealed by this depart- ment. Any change in the mechanism of any machine so approved, tagged and sealed, without the written consent of an inspector, will be considered cause for the revoca- tion of the approvel of the use of said machine. Inspector of Factories and Public Buildings. Animated Photographs Tl&e Prin- ciples and i&e8vas&££i££@© of 'Duplex Ps?©jf©<5&I©2&. A Lecture Delivered Before ike Royal Photographic Society of London. Bv Robert Thorn Haines. I do not propose to deal exhaustively with the subject of "Cinematography," nor to enter upon an explanation of the details of those well-known methods of producing "animated pictures" which are to be found in the pages of the various books compiled by authorities on the sub- ject, but rather to confine myself to the subject of "Du- plex Projection," and to refer to those existing methods, only in so far as they will apparently assist me in ex- plaining the work done and experiments I have conducted in my effort to obviate the defects which are so well known to exist in the ordinary system of projection. An important era in pictorial history was marked by the introduction of cinematography or art of reproducing animated scenes. - The physiological phenomenon of "Persistence of Vision," upon which its principle is based, was known and demonstrated long before its application to the pro- duction of living pictures. The great variety of card illusions, and the innumer- able devices which were from time to time introduced for the purpose of illustrating and exhibiting various phases of motion, were all the forerunners of the cinematograph. With knowledge of the fact that the image or impres- sion of an object persists or continues to exist upon the retina for a definite period after it has been removed, or the eye is taken from it, together with the fact that by instantaneous photography, impressions of moving ob- jects could be taken so rapidly as to make them, for all practical purposes, appear stationary, it was not difficult to obtain successive pictures of moving objects, with suffi- ■ .. ■ cient rapidity to secure the various phases of the ments, nor to devise an instrument to exhibit them so rapidly, that before one image on the retina would cease to exist, the one next in succession would take its place, and so on continuously, conveying to the mind the con- ception of continuous motion. Although the period during which the image persists or continues to remain on the retina varies from about the eighth to the twenty-fourth part of a second, according to the intensity, duration, and color of the light received by the eye, it' is evident, from what is visible, that it does not continue in full strength for that length of time. For if the image persisted in full intensity for a definite period, any obscuration of it for a shorter time would not be perceptible, but it would extend over the dark interval to the limit of its persistence, and convey the impression of absolute continuity of an evenly illuminated image. That it clearly does not do, and the supposition that the moment the light is obscured it commences to gradually disappear until it has entirely left the retina does not fully account for the dark intervals, which demand some other more satisfactory explanation. If darkness could be regarded as a condition of our vision that persists for the same time as light, the dark intervals could be ac- counted for, by supposing that the light is suddenly reduced in intensity, owing to the dark period which continues to persist in its stead. In such case we could expect the light of the first picture to persist after it was obscured, and the darkness to continue to the limit of its persistence after the light from the next picture was admitted to the screen. Darkness, which is merely the absence of light, does not admit of any such condition, but if, instead of sup- posing that the darkness persists, we consider the light only, and assume what is natural, viz., that the light takes the same time to impress itself upon the retina as it does to fade from it, we obtain precisely the same result in effect as if the darkness really did persist, and in that way the dark intervals are fully accounted for. Whatever doubt may have existed in reference to the scientific effect of the physiological phenomenon of per- sistence, or the precise action of the light upon the retina, no doubt whatever exists concerning the presence of those dark intervals which intervene between the suc- cessive pictures projected by the ordinary cinematograph, and cause the appearance of "flickering," so detrimental to the art and injurious to the eyesight of the spectators. Almost every conceivable form of shutter and means have been resorted to to minimize the evil, chiefly by reducing the dark period to its least possible extent rela- tive to the time during which the light is allowed free and uninterrupted access, or by splitting up the dark intervals, or allowing light to reach the screen to sub- stitute the dark periods while the change takes place. All that could possibly be hoped to be attained by any of these methods was a partial and not a complete re- moval of the defects; and it is very doubtful whether the short, sharp, momentary impact of the reduced Intervals,