The cinematography presupposes as essential condition that property of the human eye that is called " persistence of the images on the retine".

Indeed if an any object which we have previously fixed, suddenly disappears, we go on to see it yet or a very little interval of time, at about

1/16 of second.

This phenomenon of inertia of the image on our retine gives in the cinematography the sensation of movement by means of a determined sequence of images projected on a screen: images before registered at intervals of time between the one and the other, inferior to 1/16 of second and made them slide on a pellicle or film in which are printed the instantaneous photographies, settled frames that by the overlapping, give the sensation of the moviment if made slide on a tape, by a frequency like to that one in which had been unrolled in the movie film camera.

Actually we have movie film cameras ( and therefore projectors ) that take on at a speed of about 20 frames at second and on a pellicle of a unique lane that is with a sole track or sliding.

We are able therefore to observe, that an action fo moment developped in a second, can be suddivided in 20 frames and can be examined in only 20 images if considered at slow-motiom set ( or moviola ).

But sometime, there is the necessity to run after a particular intermadiate instant, that can form object of interest of study, of discussion or of contenting.

At the occurence, it is required movie film cameras capable to be able to go on with speed, so that to be able to uncouple the frames, therefore with a speed of sliding very elevated, but perhaps, even if possible, with a damage of the quality of the same images, qualitative, with consequent results in the projection. Thence, it is observed that the same speed of advancement, in

the recommencement of an articulated movement of an action that developpes in very reduced times, can be possible tha obtamment of a double number of images, realizing a pellicle at pired tracks, bat where the frames are alternated in the advancement, at a distance halved the one from the other to see Fig 1 drawing enclosed The advantages that are derived, can be especially two a) to have m the case considered, a movie film camera calibrated at 20 frames at second , with the same and at the parity of speed of sliding, to have the double Therefore in the re-proposition on the screen, should be eliminated nearly totally all the intervals inevitably mtercurrent between a frame and the next, so a vision very clear, b) to have the possibility, in the case of examen at moviola, to be able to dispose a double number of frames and to be able to identify with a double probability, in respect to the actual system monotrack

For the above named, let us report some examples of simple cases, but they could express an idea an aeroplane, that for convenience, let us say that flies at speed of 720 km h

720 km = 720 000 m ,

1 h = 3 600 sec , m ( 720 000 3600 ) = 200 m/s, if, as before, we consider a movie film camera calibrated at 20 frames at second, we shall have one and only one frame per each 10 m of path But along this distance could be a point of reference, formed for example by a pole of only 15 centimeters and that if the circumstance is not favourable, it could not appear not at all on the frame object of the observation

Analogously, in a match of foot-ball, a ball flung to the door at a speed of

100 km h , beating against the superior cross-piece timber and rebounding on the white line of demarcation on the ground, in the fraction of time that

can be picked up by the human eye, could be lost in the case that the frame is not in coincidence with the instant of the sight

Likewise we can say about, for example, a proiectile that pierces an apple, a rotor of a turbine that can reach also 15 000 turns7m, a shovel of an airscrew-blade, a crank of a driving shaft or of a rocket that can reach the speed of 7 700 m /s ( 28 000 km h )

Recapitulating the actual medium of television shoot, cinematographic or amatorial, base on the retaking by a siple film, wc can say monotrack and with a frequency of retake that vanes from n 20 to 30 frames at second

So by the solution proposed we can have a number of frames double or alternate

But beyond the proposition exposed on the Fig I, we could form always a duoble track, with intermediate intervals, so we shall be able to have

- a first frame, to which follows the successive at the accomplishing of 9/10 of path m height Then follows a third one that intervenes at the accomplishing of the 9/10 of the second frame, and so on for all frames that follow, to see Fig II - board A -

- a first frame to which follows the successive after the 2/3 of the path, idem as the preceding case to see Fig II - board B -

- a first frame to which follow alternatively the successive frames of '/_. in 1 To see Fig II - board C -

By really experiments we could say a solution of better efficiency or acceptance

Till now we described the solution that foresees either the "retake" or the

"projection" on the relative apparatus calibrated " At double track "

But for exigences of particular importance we could "divide" the two tracks after the retake and then "mstal" the relative frames in the succession, but

on each track, so to equalize the speed of feed in the projector, so that to be able to reach the frequency of time used in the relative retake of the event. To see Fig. II - board D-