US3832054A

US3832054A - Photographic print timer

Info

Publication number: US3832054A
Application number: US00367487A
Authority: US
Inventors: A Sable
Original assignee: Sable Photo Works Inc
Current assignee: Sable Photo Works Inc
Priority date: 1973-06-06
Filing date: 1973-06-06
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

This invention relates to a multiple-event timer that presents the user with a limited number of preselected time interval choices for two or more related events which bear a precise and known relationship to one another such that the effect of a change in the time interval for one such event has a predictable effect on its relationship to the companion events. More particularly, the instant invention relates to a timer specifically suited for use in timing the three primary color exposures of a color print being made by the tri-color printing method wherein the several available discrete time intervals presented to the user are preselected and separated from one another by the same equal fraction of a photographic stop.

Description

United States Patent [191 Sable Aug. 27, 1974 PHOTOGRAPHIC PRINT TIMER Primary ExaminerSamuel S. Matthews 75 I t 1 Arthur Sable Boulder Colo. Assistant Examinerl 11chard A. Wintercom 1 men 9 J Attorney, Agent, or FirmEdwards, Spangler, [73] Assignee: Sable Photo Works, Inc., Boulder, wymore & Kl

Colo.

[22] Filed: June 6, 1973 [57] ABSTRACT [21] Appl. No.: 367,487 This invention relates to a multiple-event timer that presents the user with a limited number of preselected time interval choices for two or more related events (5|. 35583055523432 which bear a precise and-known relationship to one [58] Fieid 36 37 another such that the effect of a change in the time 3 5 5 2 interval for one such event has a predictable effect on its relationship to the companion events. More partic- 56] References Cited ularly, the instant invention relates to a timer specifically suited for use in timing the three primary color UNlTED STATES PATENTS exposures of a color print being made by the tri-color 3.049969 8/1962 Clapp..' 355/36 printing method wherein the several available discrete 1 N 10/197l Riley et f a 355/35 time intervals presented to the user are preselected 3,672,767 6/1972 Pamleny| 355/38 and Separated from one another by the samevequal fraction of a photographic stop.

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T0 DRIVER PHOTOGRAPHIC PRINT TIMER Reasonably precise time control is necessary in the photographic print making process even when the processor is only making black-and-white prints although a full f-stop over or underexposure is difficult for most viewers to detect. ln color printing, on the other hand, accurate time control is essential because even the average viewer can easily detect a /sf-stop print exposure error while the trained observer can notice a difference of as little as one-sixth stop and less.

Unfortunately, precise time control alone, while reasonably easy to achieve, is far from a complete answer, especially to the timing of three individual primary color exposures when making a print by the so-called tri-color" exposure method. The real problems arise in connection with introducing the appropriate corrections necessary to overcome the previously observed condition of improper color balance. The first problem is knowing how much to increase or decrease the time interval for a particular color or colors at different overall exposure times. In other words, just knowing that the red exposure is too dense by a half stop is not enough when to decrease the overall red exposure at a l second exposure time means a different thing than to introduce the same correction at a 30 second exposure time. Admittedly, a table can be worked out rather easily that will tell the user what correction need be made for a /2-stop exposure error at various selected overall time intervals but to use such a table is timeconsuming and most unhandy.

The correction of a single variable as above noted is simple compared with the complex problem of correcting for a condition of color imbalance involving two or all three colors, each of which has a different overall exposure time. If, for example, the full color image is too yellow, varying the exposure time of just one of the three primary colors relative to the other two will not do the job, but instead, a suitable correction demands that both the red and green components be cut back to some degree. In the above instance, while both the red and green would, presumably, have to be cut back the same amount, this would not manifest itself in the same time interval corrections due to the fact that the overall exposure intervals for these two colors will rarely, if ever, be the same. If we add to this the further complications of having to correct one primary color more than the other or, perhaps, all three at once, one can readily appreciate that the problems become monumental. especially for the amateur photographer who seldom possesses either the skill or the patience to solve them correctly. v

The prior artphotographic timers including the relatively few that are both sensitive and accurate offerlittle help for the simple reason that they offer the user a complete range of time intervals broken up into seconds or fractions thereof from which he must select the particular intervals that will produce an acceptable print. Even if the operator possesses the requisite technical skill to go back and forth from his interval timer to a correction table tointroduce the appropriate time interval changes necessary to correct for a condition of color imbalance, to do so is quite time-consuming and troublesome.- It would. seem, therefore, that a prime requisite of a superior photographic timer would be the elimination of the complete range of possible time interval choices accompanied by a preselection of a few which would be most useful while, at the same time, providing all the control necessary to produce an essentially perfect print.

Next, the increments of time separating these preselected intervals should, if possible, be chosen such that each means exactly the same thing in terms of the shift in color balance irrespective of the duration of the overall exposure time, i.e., whether it be long or short. In other words, the increase or decrease of the overall exposure time to the next highest or next lowest preselected time interval should accomplish precisely the same color shift at an overall exposure time'of 10 seconds as it does at 40 seconds.

Finally, and most important, the preselected exposure times together with the incremental intervals therebetween for each of the three primary colors must integrate with those of the other two such that they will cooperate and enable meaningful and predictable color shifts to be made where the condition of color imbalance is the result of a combination of two orv all three colors instead of just one. Saying this another way, it is not only important that an incremental correction have the same known effect on a given color regardless of its overall exposure time, it is imperative that the increments for the timers controlling all three primary color exposures have the exact same effect on their respective colors so that a predictable cooperative relationship exists therebetween.

It has now been found in accordance with the teaching of the instant invention that these and other worthwhile objectives of a superior photographic timer can, in fact, be realized by the simple, yet unobvious, expedient of preselecting a series of time intervals for the three primary colors that bear a logarithmic relationship to one another and in which the intervals therebetween correspond to the same fractional divisions of an f-stop in all three scales as well as each scale individually.

It is, therefore, the principle object of the present invention to provide a novel and improved multipleevent timer.

A second objective of the within-described invention is the provision of a timer of the class described which is ideally suited and especially adapted for use in timing the primary color exposures of a color print being made by the tri-color printing process.

Another object is to provide a photographic print timer in which the available time intervals arepreselected.

Still another objective is the provision of a timer for photographic prints wherein the preselected exposure times bear a logarithmic relationshipto one another.

An additional object is to provide a timer for color print-making of the type disclosed and claimed herein, in which the same intervals separate the preselected times in all three time scales as well as in each scale individually and in whichsuch interval corresponds to a fractional part of an f-stop.

Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that-follows, and in which: v

FIG. 1 is a schematic view showing an electromechanical embodiment of the timer employing a notched disk as the means for activating the multicontact selector switch atpreselected time intervals;

FIG. 2 is a schematic view showing a second electromechanical embodiment in which the timing motor actuates a reed switch, the pulses of which are fed to a stepper;

FIG. 3 is a block diagram illustrating a timing circuit utilizing a pulse generator, a pulse counter to count the timed pulses from the generator and a decoder to deliver a preselected array of pulses to the selectors;

FIG. 4 is a block diagram similar to FIG. 3 but showing a synchronous motor and reed switch used as the pulse generator, a pair of steppers as the pulse counter and selector switches connected to the latter in a manner to preselect certain pulses from the array thereof;

FIG. 5 is a schematic diagram of the timing circuit shown in the block diagram of FIG. 4;

FIG. 6 is a schematic view showing the manner in which all of the selector switches are connected to the steppers in a manner to select timed intervals therefrom bearing the logarithmic relationship to one another predicated upon fractions of an f-stop;

FIG. 7 is a block diagram illustrating an electronic timing circuit of the general type exemplified in FIG. 3;

FIG. 8 is a schematic diagram of the electronic timing circuit of FIG. 7; and,

FIG. 9 is a wiring diagram showing how each of the l2-position 4-pole selector switches are connected to the output of the cascaded binary counters so as to provide a preselected set of exposure times bearing a logarithmic relationship to one another with the intervals therebetween comprising equal fractions of an f-stop.

Referring next to the drawings for a detailed explanation of the present invention and, initially, to FIG. 1 for this purpose, probably one of the simplest forms of the timer comprises an electric motor 10 of a type adapted to make one complete revolution in a total time interval that slightly exceeds the longest time interval of the preselected choices. Thus, if we select a time scale covering a total of 60 seconds, then the motor should make one complete revolution in something in excess of 1 minute, say 65 seconds. In accordance with the teaching found herein, instead of dividing the foregoing maximum time interval up into a full complement of possible choices broken down to tenths of a second as is commonly done in the prior art photographic timers, a series of preselected increments will be chosen that are arrayed in a logarithmic relationship to one another that corresponds to fractions of an f-stop. For instance, if we choose increments of one-third stop, the preselected discrete time intervals would be as follows starting at, say a minimum interval of 3 seconds: 3.0 3.75 4.75 6.0 7.5 9.5 12.0 15.0 l9.0 24.0 30.0 38.0 48.0 60.0 Now, as represented schematically in FIG. 1, a single peripherally-notched disk 12 would be driven in synchronous fashion by the motor 10 so as to complete one full revolution in 65 seconds. A total of 15 notches, I through 15, would be provided in the periphery of the disk if the above logarithmic scale is used including as the first notch, the one corresponding to zero time. Instead of the notches being equiangulary-spaced around thecircumference of disk 12, they are, of-course, located relative to the first notch in accordance with the particular time interval they represent. In the sche matic of FIG. 1, each notch is shown linked mechanically to a companion switch denominated Sd), 53.0 S48, S in accordance with the time scale. In the par ticular form illustrated, switches S S60 are of the single pole double-throw type which function upon arrival of the disk at the notch to which they are mechanically linked to momentarily shift to the open contact of the pair.

In operation, closure of the normally-open start switch 14 latches in relay 16 to turn on the timing motor 10. After enough time has elapsed for the motor to reach synchronous speed, the disk 12 driven thereby reaches notch 1 and actuates the companion switch S4) linked thereto in a manner to momentarily energize relay 18 which latches itself in. The latter relay turns on the enlarger lamp 20 at time zero.

Presumably, the operator has already determined a set of exposure times for the red, green and blue components of the finished color print from among those preselected choices made available to him. In accordance with such selections, the operator will set each of the three selector switches R22, B22 and G22 on the contact thereof connected to the switch (SI-S60) corresponding to the particular time interval chosen.

When switches B22 and G22 are actuated through the chosen contact by the S-switch connected in series therewith, they each energize a solenoid G24 and B24 in the particular embodiment illustrated. These solenoids might be used by way of example to move magenta and yellow subtractive filters into the light path in accordance with the teaching of my copending application Ser. No. 223,081, now US. Patent No. 3,797,933, issued Mar. 19, 1974, to terminate the green and blue exposures, respectively. This particular circuit is predicated upon the assumption that the red exposure will be the longest of the three, therefore, when red selector switch R22 actuates, it will deenergize relay I8 thus extinguishing the enlarger lamp and terminating the red exposure as red light is the only color that is still being allowed to pass through the subtractive filters.

The final step in the cycle is to trip switch S60 which reopens relay l6 and stops the motor 10. As it does so, the motor 10 and disk 12 will coast far enough to pass notch 15 in the latter and reset the switch S60 so that it will, once again, operate to latch relay 16 upon closure of the start switch. This feature also allows the motor to get up to synchronous speed before notch 1 is reached on the disk that actuates switch 8(1) and turns on lamp 20.

As an alternative to the above, the motor could carry three identical disks 12, each connected to its own set of switches. Such a construction would, of course, be more expensive and no significant advantage would be gained over the single-disk embodiment illustrated.

Next, with reference to the circuit diagram of FIG. 2, a second slightly different form of timer has been illustrated wherein the synchronous motor 10 carries a cam (shown schematically by broken line 12M) that is analogous to the notched disk of the FIG. 1 embodiment in that its peripheral margin is formed to actuate a single switch 28 repeatedly at each of the preselected time intervals as well as at the start of the timing cycle. A stepping switch 30 connected to the cam-actuated switch 28 responds to each closure of the latter and counts them in the usual way by stepping from contact to contact thereof.

In the specific circuit shown in FIG. 2, closure of the normally open start switch 14 pulls in relay 32 and latches it in closed position. Relay 32 along with the other relays in the circuit which will be described shortly are all of the conventional two-winding latchunlatch type, either magnetic or mechanical. When relay 32 latches in, the timing motor is energized and power is supplied to the stepper circuit. After a brief time during which the motor comes up to speed, the cam 12M carried thereby will make the initial closure of cam-actuated switch 28 which, in turn, advances the stepper onto its zero contact. With the zero contact thus energized momentarily, relay 34 latchesin turning on the enlarger lamp as before.

The red, green and blue selector switches R22, G22 and B22 are set as in the previously-described circuit on the contact thereof that represents the particular preselected time interval the operator has chosen to expose each primary color in the finished print. As before in the case of the green and blue selector switches G22 and B22, when the stepper has been advanced by the cam-operated switch 28 to the live contacts, the solenoids G24 and B24 controlled thereby will be energized to move appropriate subtractive filtration into place assuming the timer is being used to make prints by the subtractive tri-color method for which my enlarger is designed. Obviously, both the timer circuits of FIGS. 1 and 2 could readily be adapted to other color printing methods without the exercise of invention and the ones shown are intended as being merely representative of the type of circuit that can be controlled by the digital timer of the present invention.

Once again, we will operate upon the assumption that the red exposure is the longest of the three so that when the stepper advances to its live contact, the unlatch coil of relay 34 will be energized to drop it out and turn off the enlarger lamp. It is to be understood, of course, that stepper 30 will have at least fifteen stepped contacts to accommodate the 14 preselected intervals and one at the start or time zero. The intervals at which the stepper advances will be determined by the cam 12M actuating switch 28.

Once the stepper has advanced all the way to the last contact in the series (contact 14 if we assume the same set of preselected intervals set forth earlier), it will drop out relay 32 by energizing the unlatch coil thereof. With power no longer supplied to motor 10, it will coast to a point where the cam 12M leaves the camactuated switch 28 open prepared to begin another cycle. The start switch 14 has, of course, reopened and when it closes to relatch relay 32 and start the motor, the latter will be able to get up to speed before the camactuated switch closes to advance the stepper onto its zero contact.

The remaining two specific embodiments differ from those just described in that instead of generating a series of discrete pulses that already bear a preselected logarithmic relationship,-a pulse generator is used that generates a series of pulses equally-spaced in time. These pulses are then counted by a divider or counter which has a unique combination of output signals for each count within its range. The counter outputs are decoded and certain preselected counts are chosen from among the available array thereof corresponding to the particular exposure'times the operator will need to the exclusion of all others. From this preselected array, the operator'then chooses one for each color component of the final print andit is used to initiate an operation such as the one already described, namely, the termination of a previously-initiated exposure.

A block diagram of such a timer has been illustrated in FIG. 3 where reference numeral 36 designates the pulse generator keyed to the 6OI-Iz power line frequency. The equally-spaced pulses generated by the latter are fed to a pulse counter 38 where a decoder 40 picks certain pulses therefrom that bear a logarithmic relationship to one another corresponding to fractional portions of an f-stop. Two or

more selectors

42R, 426 and 42B are connected in parallel with one another to receive-the predetermined output of the decoder from which the operator makes a single selection.

FIGS. 4, 5 and 6 to which reference will now be made are directed to a specific electro-mechanical embodiment of the timer represented by the block diagram of FIG. 3. The pulse generator indicated in a general way by numeral 36 comprises a synchronous motor 44 and a magnetic reed switch 46. The motor is driven at a constant accurate speed from the 6OI-Iz power source and its output shaft (represented schematically in FIG. 5 by broken line 48) is geared down to turn at a relatively slow speed such as, for example, 120 r.p.m. A magnet (not shown) attached to this output shaft rotates at this frequency in operative proximity to the magnetic reed switch 46 which responds by opening and closing each time the magnet turns end-for-end so that two pulses per revolution of four pulses per second are generated in equally-spaced relation with reference to time. The pulses thus generated are fed to a pair of cascaded l2-position electro-mechanical stepping switches 50 and 52 connected such that switch 50 increments one position with each pulse and repeats after the 12th pulse, whereas, switch 52 increments one position after the first one completes each cycle, i.e., every 12th pulse. Thus, the first stepper 50 completes a cycle every 3 seconds and the second stepper 52 every 36 seconds. As thus designed, one has a choice of time intervals up to a maximum of 36 seconds broken down into A second equal increments since there is a unique combination of stepper positions for each of the 144 increments.

It is from this point on that the timer becomes unique among photographic timers because, instead of providing the user with a full range of discrete time intervals, the steps of which are equally spaced with reference to time and have no particular significance as far as print density is concerned, the instant apparatus preselects from the foregoing array of time intervals only those that bear a known and useful relationship to the photographic print-making process, namely, those that will yield equal changes in print density. More specifically, only those discrete time intervals are selected and made available to the user which bear a constant logarithmic relationship to one another predicated upon fractions of an f-stop It is only when this is done that the operator knows that increasing or decreasing the overall time interval by a one or more increment within the reciprocity limits of the print making material will have substantially the same effect on print density regardless of the particular overall exposure interval. In

addition, he knows that each incremental change to shorten or lengthen the overall exposure times of two or all three primary colors will result in the selfsame changein the density of the color in the emulsion layer of the print making material responsive thereto even though the overall time intervals themselves are entirely different. Furthermore, and most significant, the user is, for the first time, provided with the means by which a condition of color imbalance brought about by a mixture of two or even all three primary colors can easily and predictably be changed into its proper relationship by making incremental shifts in the colors effected which bear a known cooperative relationship to one another that is substantially independent of their respective overall exposure times.

Accordingly, the stepper positionscorresponding to the preselected time intervals chosen as above-noted from which the user can choose are wired to

selector switches

42G, 42B and 42R in accordance with the wiring diagram of FIG. 6 showing one such switch, the other two being wired identically to the one shown. The switch arms 54 and 56 (FIG. of these selector switches are live only when the preselected pulse count is reached. These switch arms are in turn connected to actuate the timed operation to be performed such as, for example, to energize relays G24 and B24 to insert the subtractive filters in the light to become operative to terminate the green and blue component exposures and to deactuate the relay 58 that is keeping the enlarger lamp lit.

Specifically with reference to FIG. 5, switch 60 is of the single-pole double-throw type operative in one position to energize the enlarger lamp 20 independently of the timer circuit for focusing purposes and in its second position to actuate the timer circuit. Switch 62 is a momentary contact switch employed to initiate the timing cycle. Closure of the latter causes relay 64 to pull in and latch through its own contacts thus starting motor 44 that actuates reed switch 46 twice each revolution. Relay 64 as well as relays 58, 66, 68 and 70 are all of the double-pole double-throw type even though not all the contacts are used.

In operation, since the motor takes a little time to reach synchronous speed, it is turned on a few pulses in advance of zero time on the

steppers

50 and 52, both of which are l2-position single-pole stepping switches of conventional design. The pulses occurring each onefourth second from reed swtich 46 advance stepper 50 through its 12 pulses, whereupon, stepper 52 advances one step with each 12th pulse of stepper 50. When the 0-0 position (zero on both steppers) is reached, relay 66 is pulled in momentarily and it, in turn, pulls in relay 68 which latches in through its own contacts and turns on the enlarger lamp 20.

If, for example. contact 4 on stepper 50 and contact 6 on stepper 52 were connected to the N contact of selector 420, this would mean that the latter contact would be live after a time lapse of 19.0 seconds which is one of our preselected time intervals. Stepper 52 will have advanced six increments corresponding to 18 seconds (stepper 50 steps a full cycle every three seconds) and four steps on stepper 50 amounting to one additional second. Then, if as assumed previously, we have preselected time intervals in /af-stop increments starting with 3.75 seconds as shown in FlG. 6, the ninth or H-S" pair of contacts will correspond to 19.0 seconds. If the green component time interval is b 19.0 seconds as set on selector 42G, then the green solenoid G24 will energize momentarily to actuate and initiate the tennination of the green component exposure, probably by interposing a magenta filter in the light path. A similar sequence is followed to actuate blue solenoid B24 at the preselected time interval for the blue component exposure to move a yellow filter in place or otherwise terminate the blue exposure. When, however, the

steppers

50 and 52 step to the time interval set on selector switch 42R, relay 58 is momentarily pulled in which unlatches relay 68 causing it to drop out and extinguish the enlarger lamp. The steppers, however, continue to advance incrementally until they reach position 5-l 1, whereupon, relay 70 is momentarily pulled in thus unlatching relay 64 causing it to drop out and turn off the motor while deenergizing the

steppers

50 and 52. These steppers, therefore, come to rest a few positions before position 00 giving the motor time to get up to synchronous speed before the timing cycle is initiated.

Next, with reference to the remaining figures of the drawings, specifically, FIGS. 7, 8 and 9, the fourth and final version of the timer, a fully electronic one, will be described in detail. In the latter, both the generation of the pulses and the counting thereof is done electronically instead of electro-mechanically as was the case in the version just described.

The pulse generator 36m shown in the block diagram of FIG. 7 comprises a voltage comparator which generates a pulse with each positive zerocrossing of the 60l-lz power line voltage which, of course, occurs every 1 /60th of a second. The pulses thus generated are then fed to a divide-by-IS counter 38m that reduces the pulse count to 4 per second. The /1-second pulses then go to an 8-bit binary counter 40m consisting of eight cascaded flip-flops. From this arrangement results 256 unique combinations of flip-flop outputs thereby providing a selection of possible time intervals up to 64 seconds in /r-second increments. For each position, these selected lines are ANDed together, and the output thus joined is used to actuate the desired operation at the selected time for each selector switch 42Gm, 42Bm and 42Rm as will appear presently.

In the schematic diagram of FIG. 8 to which detailed reference will now be made, the commerciallyavailable voltage comparator 36m is a conventional integrated circuit voltage comparator such as industry type LM 311. Divide-by-l5 counter 38m comprises three 4-bit binary counter integrated circuits 72a, 72b and 720 such as, for example, type SN 7493. Reference numeral 74 has been chosen to designate a 5-volt integrated circuit voltage regulator such as type SN 75451. The selector switches 42Gm, 42Bm and 42Rm are 12- position 4-pole selector switches, preferably of the conventional multiple-pushbutton interlocking type. Interposed between these selector switches and the green and blue solenoids G24 and B24 are integrated-circuit dual high-current drivers 76 and 78 such as type SN 75451, both of which have been shownin FIG. 7. Reference numeral 80, on the other hand, identifies a quad 2-input NAND gate integrated circuit such as type SN 7400, whereas, 82 and 84 are dual 4-input NAND gate integrated circuits such as type SN 7420. Relay 86 is one having a l2-volt coil and single-pole single-throw normally open contacts.

With these specifics concerning the circuit in mind,

86 thereby turning on enlarger lamp 20. This same change in state of the flip-flop also results in the resetinhibit inputs of the counters 72a, 72b and 720 going low thus permitting them to begin counting the pulses generated by comparator 36m from the 6OHz line. The counter string consists of a divide-b'y-l counter 38m comprised of counter 72a together with feedback gates including half 82(1) of NAND gate 82 andone-quarter 80(3) of NAND gate 80 followed by an 8-bit binary counter comprising 4-bit counters 72b and 720 cascaded.

When the binary counter string 40m reaches the count correspondingto the particular choice of preselected intervals available on selector switch 42Gm, the four inputs of the NAND gate 82(2) comprising the remaining half of gate 82 all go to high simultaneously causing driver 78(1) which is half of NAND gate 78 to turn on momentarily thus actuating the green solenoid G24 to terminate the green exposure by interposing a magenta filter in the light path as before.-

Similarly, when the binary counter string 40m reaches the count corresponding to the chosen time interval from among the preselected ones available on selector switch 42Bm, the four inputs to the NAND gate 84(1) that comprises half of NAND gate 84 all go high simultaneously causing driver 78(2) which is the remaining half of NAND gate 78 to turn on momentarily thereby actuating the blue solenoid B24 to tenninate the blue component exposure such as by interposing a yellow filter in the light path.

Finally. when the binary counter string reaches the count corresponding to the time interval chosen from among the preselected times available on selector switch 42Rm, the four inputs to the other half 84(2) of NAND gate 84 all go high at the same instant causing flip-flop 80 to revert back to its original state. This results in driver 76 turning off to drop out relay 86 and extinguishing the enlarger lamp to terminate the red exposure, the blue and green exposures having been terminated previously. When flip-flop 80 changes state as above mentioned, the reset-inhibit inputs of the counters go high thus resetting them to zero and holding them there. The timer is thus readied for another cycle.

In conclusion, FIG. 9 shows one of the three selector switches 42 together with its four-input NAND gate. All three of the selector switches 42Gm, 42Bm and 42Rm are wired identically although the output of the latter is used to extinguish the enlarger lamp 20 while that of the first two is employed to bring a subtractive filter into the light beam. Actually. of course, while we have assumed that the red component is the longest of the three exposures for convenience sake, this neednt be true and either of the other twocould havebeen used. Likewise, while the timer has been described as it would be used to make a print by the tricolor subtractive technique, it should be perfectly obvious that it is equally adaptable to other color printing techniques as well as black-and-white.

FIG. 9 reveals the manner in which the selector switches 42 wouldbe wired to take the four pulses per second from the cascaded binary counters and make available to the user the preselected pattern of time intervals predicated-upon fractional f-stop increments beginning with 3.75 seconds and going all the way up to 48 seconds where every third increment is doubled.

In the foregoing description, the various timer embodiments have been designedaround a set of preselected time intervals bearing equal fractional increments amounting to either Vs or Af-stops to one another, however, it is apparent that other fractional increments can be used without the exercise of invention. It is also significant that the total range of preselected times be chosen such that no serious reciprocity failure occur in the print making material. In other words, by preselecting a range of times for the operator that are no shorter than 3 seconds or so and no longer than approximately seconds, then the preselected equal fractional increments produce essentially the same response in any of the emulsion layers of the print making material-at the minimum as well as the maximum avail able exposure times. While it is undoubtedly possible to compensate for the known variations in response of the emulsion layers of the print making material by lengthening the already unequal intervals for the long exposure times while foreshortening those that are quite short, by far the simplest and more practical approach is to limit the range of preselected choices to that wherein the equal fractional f-stop increments remain valid and evoke essentially the same response in the emulsion.

What is claimed is: I

l. The photographic timer which comprises: pulse generating means operative upon actuation to produce a series of discrete timed pulses; pulse-counting means connected to thepulse-generating means operative to receive the timed pulses and repeatedly count same in cyclic fashion; decoder means connected to the pulsecounting means adapted to discriminate among the timed pulses and select therefrom those bearing a logarithmic relationship to one another amounting to fractional parts of an f-stop; one or more pulse-selecting means connected to the decoder means, each operative upon actuation to choose a particular pulse from among the preselected array thereof; and, triggering means connected to each pulse selecting means responsive to the particular pulse chosen by the latter operative to terminate the timing cycle upon expiration of the chosen time interval.

2. The photographic timer as set forth in claim 1 in which: the pulse-generating means produces discrete pulses having equal time intervals therebetween.

3. The photographic timer as set forth in claim 1 in which: the pulse-generating means cycles approximately once a minute.

4. The photographic timer as set forth in claim 1 in which: approximately one minute separates the minimum and maximum preselected time intervals with the minimum being greater than a. second and the maximum being less than 2 minutes.

5. The photographic timer as set forth in claim 1 in which: the range of preselected time intervals extends from a minimum of approximately 3 seconds to a maximum of approximately 64 seconds.

6. The timer as set forth in claim 1 in which: at least two pulse-selecting means are connected to the decoder means and are independentlyresponsive thereto.

7. The timer as set forth in claim 1 in which: at least two pulse-selecting means are connected to the decoder means; and, in which the preselected time intervals available to each of said pulse-selecting means from the decoder means are chosen such that incremental changes of the same magitude in two or more of said selecting means will evoke essentially the same response in the appropriate emulsion layer of a multilayer print-making material irrespective of the overall time intervals to which said selecting means are set.

8. The timer for timing the component exposures of a color photographic print which comprises: means connectable to a source of electrical energy operative upon actuation to repeatedly generate in cyclic fashion a series of discrete pulses bearing a logarithmic relationship to one another such that the intervals therebetween constitute equal fractional parts of an f-stop; means comprising a selector switch for each color component adjustably connected to said pulse-generating means adapted upon actuation to pick a particular pulse during each cycle from the preselected array thereof independently of the other selector switches; and, means connected to each of said selector switches responsive to the particular pulse chosen thereby so as to terminate the component exposure at the selected time within the cycle.

9. The color print timer as set forth in claim 8 in which: the pulse-generating means comprises a motor and a notched disk operatively connected to the motor one contact in the array thereof.

Claims

1. The photographic timer which comprises: pulse generating means operative upon actuation to produce a series of discrete timed pulses; pulse-counting means connected to the pulsegenerating means operative to receive the timed pulses and repeatedly count same in cyclic fashion; decoder means connected to the pulse-counting means adapted to discriminate among the timed pulses and select therefrom those bearing a logarithmic relationship to one another amounting to fractional parts of an f-stop; one or more pulse-selecting means connected to the decoder means, each operative upon actuation to choose a particular pulse from among the preselected array thereof; and, triggering means connected to each pulse selecting means responsive to the particular pulse chosen by the latter operative to terminate the timing cycle upon expiration of the chosen time interval.

4. The photographic timer as set forth in claim 1 in which: approximately one minute separates the minimum and maximum preselected time intervals with the minimum being greater than a second and the maximum being less than 2 minutes.

6. The timer as set forth in claim 1 in which: at least two pulse-selecting means are connected to the decoder means and are independently responsive thereto.

7. The timer as sEt forth in claim 1 in which: at least two pulse-selecting means are connected to the decoder means; and, in which the preselected time intervals available to each of said pulse-selecting means from the decoder means are chosen such that incremental changes of the same magitude in two or more of said selecting means will evoke essentially the same response in the appropriate emulsion layer of a multi-layer print-making material irrespective of the overall time intervals to which said selecting means are set.

9. The color print timer as set forth in claim 8 in which: the pulse-generating means comprises a motor and a notched disk operatively connected to the motor so as to make a single revolution in a total elapsed time that exceeds the maximum of the preselected time intervals, the notches in said disk being spaced around the rim thereof in a logarithmic fashion corresponding to the chosen fraction of an f-stop; and, in which said selector switches each have a plurality of contacts, one of which is connected to each notch in the disk, and an adjustable switch arm movable upon actuation to any one contact in the array thereof.