US2372346A - Photographic printing - Google Patents

Description

March 27,1945. R. TERRANEAU ETAL 2,372,346

PHOTOGRAPHIC PRINTING Filed Feb. 4, 1942 3' Sheets-Sheet l ,Zzaveniigrs R; TERRANEAU EfAl. I 2,372,346

March 27, 1945.

PHOTOGRAPHIC PRINTING Filed Feb. 4, 1942 l 3 Sheets-Sheet 2 .26 z/ GZUZOIRS 11?. 2 6122" an ea 10 WW i g Patented Mar. 27, 1945 I 2,3723% rnoroomrnro PRINTING Randal Terraneau, Kingston Hill, and James Leslie Stuart, London W. 1, England Application February 4, 1942, Serial No. 429,566

- In Great Britain February 7, 1941 1 Claim.

This invention relates to photographic printing and more specifically to printing from kinematographic films.

Owing to variations in actinic conditions during the exposure of various sections comprising most kinematographic films and to the resulting variable density of the film negative, it is desirable, in order to obtain a print whose light level does not vary considerably throughout its length, to compensate for this varying density.

Various methods have been employed for this purpose hitherto, for example, a variation in the current passed through an electric lamp provid ing light for printing, the variation being appropriate to the compensating light value required; this method has brilliance of the lamp alters the colour values emitted in addition to merelyaltering'the intensity of the light.

Another prior method is to cause the printing light to pass intermittently through a film negative and a control film which latter has been formed in sections mechanically attached together to form a strip or length of film, the individual portions of which have the required degree of obscuration. This method has the drawback that it can onlybe used with an intermittent step movement printer since the control film must be moved to its next position during'the shutter covered period. Intermittent step movement printers cannot be run faster than approximately 40 feet per minute.

Another prior method is to employ a mechanical gate the width of opening of which has to be set by hand for each individual section of the film. This method has the drawback that the speed of printing is controlled by the skill of the operator and consequently in practice the maximum speed of transit'of the film during printing cannot be made to exceed about 60 feet per minute.

A further prior method is to use a translucent strip which is moving continuously during the printing operation at one fourth the speed of the negative film. Strips of each width are made photographically in long lengths, these being stored for future use. Strips of the required widths are then joinedin suitable lengths in synchronism with the picture negative by winding over a synchronising. device. This method entails much handling of the valuable negative film. Furthermore, owing to the fact that the widths vary by only afew thousandths of an inch and that the photographic fog-is. liable to vary'from time to time in the manufacture-of the lengthsof the drawback that change of' translucent strip uniformity of results is most difficult of achievement.

The main object of the present invention is to provide an improved method and means for taking photographic prints of kinematograph films with great rapidity the prints possessing substantially uniform light value throughout, irrrespective of variation in density of different sections of the film.

Referring to the accompanying drawings:

Figure l is a front view of part of one convenient form of apparatus embodying the present invention.

Figure 2 is a side elevation thereof.

Figure 3 is an enlarged plan view.

Figure 4 is a vertical sectional view on the line A-A of, Figure 3, whilst Figure 5 is a vertical 3-15 of Figure 3.

In carrying the invention into effect according to one convenient form illustrated by way of example in Figures 1 to 5, we provide an optical system projecting a beam of light from a lamp 42 through a lens 43 and then vertically upwards through a prism a, through a further prism b and thence through a slot 0 over which the kinematograph film d from which a print is to be taken,, and the print e itself are caused to travel. The film together with the print are carried on spools and are fed forward together at a constant speed.

Interposed in the path of the beam is a control film 1 carried on spools 30, 3| and furnished with shift apparatus described below. The control film comprises a strip of film furnished at the centre with a series of adjoining photographically produced translucent sections forming a continuous strip running from end to end of the film. The widths of the various sections, however, vary throughout the length of the film in accordance with the desired degree of obscuration of the beam and the number of sections is equal to the number of diiferent light levels in the negative.

Whilst printing of a particular section of the kinematograph film din which the light value is substantially constant is taking place, the con trol film f is stationary and a predetermined degree of obscuration of the beam results, but when a succeeding section of the'film is being printed in which, say extra printing light is required to compensate for increased density of this section, a wider-apertured frame or section in the control film strip will have been shifted into place in the sectional view on the line path of the light beam.

The shift mechanism for the control film f comprises a constantly running shaft 9 upon 'up and rotated contacting with brushes q by means of which current is supplied to the coil of the clutch when it is desired to cause the armature 7' to be picked with the clutch body. The armature a is rigid within a collar 1' on a sleeve s mounted in bearings t u on the shaft g.

The sleeve s carries loosely two disc members In operation, the driving shaft is caused to rotate continuously in one or other direction ac cording to whether the film d and print e are moving from right to left in Figure 1 or vice versa, but so long as the control film f is desired to remain stationary to intercept a particular fixed degree of obscuration in the path of the light beam, the armatures 5, 5a. are held stationary by the springs associated therewith and the particular projection 3, 3a is held by its latch (4); the Maltese spur toothed gearing H3, -|5 and the 50- toothed wheel 29 thus remain stationary.

w, w, and each of these disc members has an integral collar :1), an and is furnished with a pin 1 the pins are connected by tension springs z with a radial pin 2 rigidly fixed to a sleeve s. The disc members are cut away at one part of the periphery to form projections 3, 3a, oactin with stop members 4, 411 formed at one end of a pair of spring-urged see- saw levers 5, 5a pivoted at 6. The radial pin 2 projects through slots in the collars at, $31, one of which slots is shown at 9 in Figure 4. The sleeve 8 carries rigidly a driving disc l0 and integral collar H, the disc being furnished with two radial teeth l2 and depressions I3 for engaging teeth'l4 on a driven member comprising a disc l5 and integral collar 16. The

disc I5 is coupled by pins l9 and spring-urged plungers toa further disc 2| having further teeth l8 and the disc I0 carries a projecting pin I! for cooperating with spaces between said further teeth l8. Y a

The disc I5 is fast on the driven shaft 22 whilst the disc 2| is loosely mounted thereon. The collar v on the shaft g acts as anabutmerit for a spring 23 abutting a D-washer 24 whereby axial pressure is applied to a friction washer 25 abutting a collar 26 screwed to the sleeve s.

The shaft 22 is mounted in bearings 21, 28 in the frame 0 and carries rigidly a toothed wheel 29 having, say, 50 teeth for engaging marginal perforations in the control film 1 which iscarried on spools 30, 3| ,mounted on members 32, 33 respectively. These members 32, 33 are rigid on shafts 34, 35 carrying gear wheels 33, 31 driven by a common gear wheel 38 rigid on the shaft 22.

It is preferred to employ a large area of control film for each section and to avoid any joint or obstruction, thus ensuring that any minute spots or imperfections in the translucent part of each section of the control film do not affect the printing light intensity. s

The length of each section of the control film conveniently embraces five marginal perforations, the perforations being engaged by the teeth of wheel 29.

A pair of spring-urged levers carrying rollers 39, 39a at their free ends are provided, the rollers engaging one edge of the kinematograph film d and the levers serving to control electric circuits for actuating two solenoids 40, 4|. The solenoid 43 controls the see-saw lever or armature 5 to release the projection 3 whilst the solenoid 4| controls a similar armature 5a to release the projection 3a. The edge of the film d engaging the roller 39 is furnished with shallow notches at appropriate positions along its length so that as the film moves past the roller the latter enters the individual notches and thus causes the springurged levers to cant and so close momentarily the circuits of the solenoids 40, 4| when shift is to takeplace.-

Assuming the rotation of the shaft 9 to be in clockwise direction as viewed from its driven end in Figure 3, then owing to the friction introduced by the washer 25 the sleeve s and the members thereon will tend to rotate clockwise. They will, however, be prevented from movement by the latch 4 lying in the path of the projection 3.

When a notch in the edge of the kinematograph film d permits the controlroller 33 to drop thereinto, a circuit is closed to energize the clutch h and also to actuate stop latches. The armature or clutch plate 7' will thus be brought into frictional driving contact with the clutch h and will commence to rotate. The sleeves, disc H) and discs, w, 1.01 will also commence to rotate and in due course the pin I! on disc Ill will strike one of the teeth l8 and thus load the mechanism i9, 21). After a short Period of time the teeth l2 engage the teeth I and the disc l5 will rotate through /10 of a revolution; the disc I5 in turn will rotate the wheel 29 through a corresponding amount, thus feeding forward the control film The sleeve s continues to be driven forwards by the friction washer 25 until the projection 3 meets the pin l1 serve to limit the movement of the disc 2| thus ensuring that the wheel 29 comes to rest in accurately predetermined positions after each progression.

The members 32 and 33 are partially rotated by gear wheels 38, 36 and 31 as the movement of the shaft 22 takes place.

After the control roller 39 has been forced outwards to resume its normal position against the edge of the kinematograph film, no further movement of the control film 1 takes place until the next notch in the edge of the film d comes into register with the roller 39.

The feeding motion of the control film j will take place very rapidly indeed owing to the action of the continuously running-clutch h and the associated mechanism,'the shift in practice being completed during the interval occupied in the kinematograph film d being moved forwards from one frame to the next. J

Owing to the control film strip changing from one section to another abruptly with no obscuring of the light, the effect, when a change is taking place, is that of a fade from one light value to another, and owing to the change is made'very rapidly and taking place at a frame line thelight change is not noticeable in the final projection print. 7

The provision of the resilient mechanism 2, 2, l9 and 20 facilitates the rapid action desired whilst reducing noise and wear of themechanism.

The driving shaft 9 may be operated in a clockwise or counter-clockwise direction as desired according to the direction in which it is desired to pass the kinematograph film d and. print e through the apparatusfor printing and one or. other of the rol1ers 39, sac; the stopsa'nd projections 3, 3a are operative according to the selected direction of rotation. Whilst in the above exampie a notch in the edge of the film negative is employed for controlling the shift of the control film, other means may be employed. For instance, the thickness of joints in the negative or metal staples suitably fitted to the negative may be utilized to actuate electrical contacts to the circuit of the clutch h and of the solenoids 40, 4 I.

It will be appreciated that in accordance with the present invention photographic fog occurring during the formation of the control film is distributed over the whole of the control film and thus has only a. negligible eiiect upon the controlling efiect produced.

We claim:

Apparatus for printing a motion picture film from a negative having a plurality of sections of different light levels embodying means for moving the positive and negative films with a uniform motion, a source of light of fixed intensity, a film strip mask interposed between said films and said light source, a plurality of translucent sections of uniform density but difierent widths on said mask equal in number to the number of light levels in the negative, intermittently operated shifting mechanism for said film strip mask comprising switch contacts actuated by said negative, a constantly rotating shaft controlled by said switch contacts, a driven member and an electromagnetic clutch between said driven member and said shaft, and wherein a plurality of mechanical stops co-acting with said shifting mechanism and an electromagnetic relay co-acting with said mechanical stops are provided, and means for starting and stopping said shifting mechanism at intervals dependent upon the lengths of individual translucent sections on said mask.

RANDAL 'IERRANEAU. JAMES LESLIE STUART.

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