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times to give a soft contrast, for 5 times to hydroquinone has got level, and is identical give a medium or correct contrast, and for 8 in all the tones, while at 6 minutes it is the times to give an exaggerated or hard contrast. denser of the two in all the tones. The advantage of this plan of timing develop The different types of developers have, there. ment is that the same contrasts can be secured fore, different ways of going to work ; but I at another time even if the temperature is have never been able to discover that the final different and if the developer has not the same

result differs if each is carried to the same activity as regards alkali.

stage of development, and no bromide is used. I do not propose to make this paper a com I show strips developed by five different deplete practical exposition of this factorial velopers to illustrate this, each carried to the method of development, for I have recently same steepness of gradation. Even with hydropublished a handbook on the subject; and I quinone, which brings out detail last of any, I will pass on to examine those variations in the find (provided no bromide is used) that the character or proportions of the developer which faintest detail rendered by the exposure is in the past have been relied upon to secure fully brought out when development is carried control of results.

far enough for a suitable contrast for printing It may be noticed that I have spoken of the on P.O.P. A developer exceedingly strong in main course of development quite independently pyro seems to have slight restraining erect, of the developing agent used. This is because and holds back the lower tones in the early I find that all developers, after all the tones | stages. have appeared, and leaving fog out of the I have explained at greater length the differquestion, do the same proportion of work on ences between developers in the Photographic the different tones and attain the same result | Journal, April, 1900. if the right time is allowed to each.

I must, however, note that my experiments

have not included ferrous oxalate developer, COMPARISON OF DEVELOPERS.

which has the reputation of giving a lower But in comparing the different developing speed. It has, however, practically gone out agents, some (such as hydroquinone and strong of use for negative work, and is being pyro) will be found to give density in the upper abandoned even for testing purposes. There tones quickly and to bring out detail in the are also some indications that a few exceptional lower tones slowly. Another class of developers, plates are a little more sensitive to a particular as metol or rodinal, bring out all detail very | developer, but this variation seems scarcely early in the total stages of deveiopment, while sufficient to have any bearing on practical density in the upper tones seems to follow

work. slowly. I show on the screen three exposed slips each of three gradations, developed

INFLUENCE OF BROMIDE. in rodinal, i grain pyro, and 8 grains pyro The restraining influence of a bromide in the respectively, and each taken out the moment | developer has been explained by Hurter and the lowest tone had appeared. The rodinal | Driffield in the Photographic Journal, July, has only attained a very feeble density in the | 1898. They explain how its “ holding back” upper tone, the 8 grain pyro a considerable influence on the lower tones is chiefly exercised density, and the i grain pyro an intermediate in the early stages of development, and beamount. After this commencement, all three comes less and less as development proceeds, strips would pass through exactly the same until at an advanced stage of development the stages of contrast. I should leave in rodinal for result with bromide is exactly the same in 40 times appearance, in i grain pyro (no all gradations, as if the same plate were bromide) 18 times, and in 8 grain pyro (no | developed without bromide and carried bromide), 6 times appearance, in order to to the same steepness of gradation. Even fog attain the same final result, and these figures | is only held back by bromide in the early (40, 18 and 6) would be the multiplying factors | stages of development. This explains many for these developers.

of the perplexing differences of experienceI also show strips developed in metol and especially as regards speed of plates—which hydroquinone respectively, ove strip of each have occurred between different experimenters. being taken out of the developer at 1, 2, 3, 4, | I show on the screen a series of slips illustrating 5, and 6 minutes respectively. It will be seen this point. that metol is very much ahead in stage of The “holding back” power of bromide has development at 1, 2, and 3 minutes, at 5 minutes ! in practice by far the greatest effect with deve

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lopers of low multiplying factor, such as hydro- | balanced one. Changes in the amount of quinone and strong pyro, for these have already alkali alter the speed at which development a tendency to hold back detail until late in deve proceeds but have no other effect on the gradalopment, and the two combined “holding tions, except that an excessive amount is apt back” tendencies are sufficient to keep back to cause fog. the lower tones until a steepness of gradation quite sufficient for printing purposes is reached.

OLD METHODS OF CONTROL. Fig 6 illustrates graphically the action of | I continue to see, that at Photographic bromide in the developer, the upper illustra- Society demonstrations, beginners are advised tion representing an imaginary section of the to “feel their way" in development, to begin

with a small proportion of alkali, and add Fig. 6.

more in course of development. Not the smallest power is conferred by the proceeding, for the stages of development follow exactly the same course as if a standard solution were

used from the commencement. copie

Let me also consider the procedure which

the maker's instructions and the text-books A B C

have advocated for dealing with over and densities of an exposed plate developed under exposure with pyro soda developers, without bromide, and the lower illustration when unknown beforehand. the same slip developed for the same time in It is usually advised that when the lower the same developer with bromide added. It tones appear so slowly that under-exposure is will be seen that the same steepness of feared, the developer should be diluted and gradation has been attained with both more alkali added “to bring out detail.” On developers, but that the bromide has lessened the other hand, if all the tones come out in the density in all the tones, and altogether such rapid succession that over-exposure is prevented the lowest tone from appearing. | revealed, the traditional advi

revealed, the traditional advice is to add more With longer development, however, the lowest pyro at once--say, 2 grains to the ouncetone would come out, and the other tones and an equal quantity of bromide, or else mix increase in density to just the same extent as up and apply a new developer exceedingly if no bromide were present. In these rough strong in pyro and bromide. It is certain that graphic diagrams, which are not intended to such a developer has a great power of holding be exact, I have omitted the curves of under back the lower tones and altering gradation and over exposure.

! when it is used from the commencement. The important part to remember is that this į But I have never been able to discover that holding-back power is not exercised after the any such selective power exists when once lowest tone has appeared ; and it is there- | these lower tones have appeared, or that the fore useless to add bromide some time after methods I indicate above, and which are usually development has commenced. Most com- i termed tentative development, confer any power mercial plates of the present day develop

which cannot be equally well exercised by sufficiently free from fog without the addition using a standard developer from the comof a bromide, and I regard its use as quite

mencement. unnecessary. Even in making lantern slides

The following are the details of a comparaI have found that brilliant results can be tive trial which I show on the screen. A Paget secured without bromide in the developer. XXXXX plate was exposed in a long series of

gradations, and cut up into strips which were WELL-BALANCED DEVELOPERS.

simultaneously developed in a two-grain pyro With each developing agent there is a soda developer- no bromide, some in one dish, strength which experience shows to have the the remainder in another. The first tone most useful power without being in excess. appeared in 40 seconds, and as soon as all the This is usually from 2 to 4 grains to the ounce. tones were out (in 150 seconds) the following There is also a proportion of alkali which gives | alterations were made, being previously got sufficient energy without tendency to fog. This ready in measures. To the first set of strips proportion with soda carbonate is about five or (marked ( for supposed over-exposure) two six times the weight of the developing agent. | grains of pyro and two grains of bromide A developer thus proportioned is a well per ounce were added. To the second

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set of strips (marked U for supposed | perhaps in most cases on account of ease and under-exposure) double the previous amount of simplicity, without knowledge that it was the alkali, and an equal bulk of water was added. | theoretically correct proceeding. I mention

The strips were taken out of each dish at this because I notice that several photointervals, and afterwards compared to see if graphers in speaking of the results attained the gradations had been altered by these by roll film developing machines seem to think proceedings. There was no evidence of control it is a new thing to attain uniformity of results by any such alteration other than that by developing the whole roll at once. given in both cases by length of development. If known beforehand over-exposure can be I compare one O and one U strip, both having compensated for by using a short factor deattained about equal contrast. All the tones veloper with bromide. Under - exposure if are also equal, a little fog being added in the known beforehand can not be improved; the case of l'.

use of more alkali or of a long factor developer

such as rodinal does not bring out any more COMPENSATING FOR VARIED EXPOSURES. detail than the ordinary formula (no bromide)

It was Hurter and Driffield who proved that gives. The only hope lies in heated developunder and over exposures ought to receive the

ment. same time of development to secure the same contrast.

SUMMARY OF PRINCIPLES. The strip of gradations on the screen, having alongside bits of over, medium, and under Different developers vary in way of going exposed negatives all developed for the same to work, and speed of working, but not time, illustrates this. The over-exposed negative (bromide influence excepted) in final result. utilises the upper tones of the series, and is' Variation of the composition of a developer denser throughout. The under-exposed nega. (bromide influence excepted) does not influtive utilises the lower tones of the series and is ence final result. thin throughout; but, except where they fringe / The bromide influence is not well under on the extreme tones which are under or over control, and cannot be exercised after all the range of the plate, both negatives give the tones have appeared. Bromide is best prints of much the same detail and steepness omitted from the developer, being unnecesof gradation. In this time development, sary. The influence of time is quite sufficient therefore, the exposure decides the density of for all control required. the negative.

I have often developed six negatives in a dish together--snapshots, interiors, and land

The Two TIME METHODS. scapes mixed; observed the time of appear ! There are two ways of deciding the time to ance of the average high lights of the series develop, both depending on a previous trial. (ignoring especially over-exposed high light, The first is my own factorial method in which such as a window in an interior), and developed the method makes correct allowance of most for the fixed multiple of this time, knowing i changes in the developer, for (usually) different that a similar amount of contrast would be kinds of plates or films and-most important-secured in all the negatives. No doubt the for variations in temperature; it also allows use of an actinometer (my own exposure for using the developer a second time. The meter) in gauging the exposures helped second is the Hurter and Driffield method towards the uniformity of result; but a very lately followed in film developing machines--of considerable variation of exposure is allowable, I developing for a fixed time with a fixed the over-exposures in such a series being dense, !' developer. With this plan it must not be and the under-exposures thin.

forgotten that the time is only right for that When I have had rollable films to develop, | particular plate or film, and for exactly one I have also followed the same plan of timing, | composition of developer used for the first developing the whole roll at once.

time, and for one temperature. The variation In fact, it is with rollable films that the for temperature can, no doubt, be given in a method of developing different exposures for table, but if it is ignored-as one demonstrator the same time has come into general use. ! seems to have advised --summer results will be Probably nine-tenths of the rollable films de- ' very different from winter results. A second veloped in the last year or two have been de- ' use of the developer, or its dilution, also veloped without cutting up the roll at all,, requires an increase in the standard time.

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MECHANICAL APPLIANCES.

before there was any change in the shadows. The In carrying out principles certain appliances

diagrams tended to show what he thought Mr.

Watkins would like to show rather than the fact are often helpful. With my factorial method,

which he demonstrated in the actual experiments, for instance, I devised a clock for the dark

With regard to the control obtained by the use room with a ten minute dial and large minute

of bromide and by altering the concentration of divisions, as an ordinary watch, even a stop

the developer, he thought a good deal of control watch, is not convenient. It is called the

could be obtained; and, indeed, Mr. Watkins's Eikronometer and has a calculator for giving the i experiments seemed to demonstrate this. The time to develop. It is a great convenience and tendency of many people in the past appeared to its use has much increased lately. An ordinary have been to imagine that a good deal more control metronome, or a half second chain pendulum, was obtained than was the case ; but the tendency is a great help in counting seconds for the now he thought was in the opposite direction, people appearance of the image, either being better denying that one had control at all. The latter than a stop-watch. But I have always frankly

fact, however, was amply proved by Mr. Watkins, explained that all the benefits of my factorial

who had explained in a fair way that one could method can be obtained, although not so con

get over the difficulty of over-exposure, if one only

knew the fact beforehand, by the introduction of veniently, with an ordinary watch. I, there. I

bromide. But it was said that bromide was of little fore, feel no hesitation in referring to a similar

use unless put in at first. That seemed to him, fact with regard to the two film-developing

(Mr. C. Jones) a statement which was very difficult to machines recently put on the market by two

prove. If one started development and washed firms. They, no doubt, appeal to those who do not off the developer before it went too far, then i' wish to use a dark room ; but exactly the same was possible to substitute a slow acting developer. results can be attained in a dark room by At any rate, it was difficult to prove that it was not holding the whole roll of film in a U-shaped possible. With regard to developing a long series loop and see-sawing it, first through a bowl of negatives for the same time and getting use. of water, and secondly through the developer

ful results, that had been argued a good deal in a basin for the standard time. These

lately, and he thought the two extremists were machines, of course, can only carry out the

both wrong. Under certain circumstances, if one

developed negatives having various exposures for H and D time method, not my factorial plan.

the same time there would be obtained many In developing films it is important not to stint

spoilt negatives ; but if negatives all tended the bulk of the developer. It is possible to use

to under-exposure, which was the usual case in so small a quantity that its developing power

kodaks and such like cameras, it was impossible in is exhausted before the requisite work is done.

many cases to over-develop. There was no further In fact if negatives always contained the same change unless the film remained so long that there was proportions of high light and shadow it would fogging, and the fogging could be easily distinguished be quite possible to control the steepness of from the developing stage. He understood Mr. gradation by limiting the total amount of Watkins tu say that one could deal with overdeveloping salt.

exposure but not with under-exposure. He thought that quite wrong, as Mr. Watkins himself appeared to have shown. Of course that which was not on a plate could not be developed from it, but in many

plates there was a tendency to get a great density DISCUSSION.

in the high lights before the detail and shadows bad Mr. CHAPMAN JONES said he had learnt much appeared, but by using a judicious developer, which from the paper, although a great part of it travelled brought out the details first, a harmonious range of over old ground. But when Mr. Watkins made gradations could be obtained, and the operator could a diagrammatic representation of wbat had taken stop at any stage he wished. place in development, he osten failed to represent fairly what he had demonstrated by his Mr. J. H. GEAR said he did not hold with hard experiments. One of the first diagrams indicated and fast time development, but whenever he had the course of development, and showed how a certain adopted time development he bad always succeeded number of particles, after exposure by light were, with his plates. A very considerable advantage in during development, reduced in a certain proportion, the timing of development was found when dealing and by further development in a further proportion. with tricolour work. He did not know how it was Mr. Watkins, however, showed that under many possible to develop three negatives with equal conditions of development the particles were not all opacity where there was a different range of giaacted upon simultaneously, but that there was a dations, so to speak, caused by the various colours, considerable amount of action in the high lights and he felt that the timing method under such circum

shown.

stances was the only reliable system in order to get strange to say that the results produced could not be the three colours at their correct opacity. With altered and varied, and he said so with the more regard to the alteration in the factorial time, he had confidence after what he had heard that evening. He found plates of the same manufacture vary somewhat, thought if there was lacking proof that control was for instance, Lumiere's A. plates, and their B. plates, possible and existed, that proof had been furnished by and the plate sensitive to red. Taking the factor of Mr. Watkins himself. With regard to the addition 4 for the A. plate and also for the red plate, that of bromide after the development had commenced, did not give the same opacity as the green plate ; | he understood the reader of the paper to say the and in order to develop those plates with the factor, result of his work had been to convince him that no be bad found it absolutely necessary to take 4 for the saving alteration could be brought about by the blue plate, 4 for the red plate, while 3 gave the same addition of bromide once development had com. opacity for the green plate. He thought it must be menced. Such an experience was opposed to his own. admitted that there was not the control in development which had been previously imagined, if one Mr. FRIESE GREENE agreed that the bromide in adhered to the pyro and soda developer. He the developer had only a kind of mechanical, and not bad no doubt that bromide had but little effect a chemical action, but he wanted to bring before the after once commencing development, and he would meeting the fact that if the continuous electric not expect to get the control in the development by current were introduced at the beginning of the the addition of bromide. but by the addition of sodium development where bromide was used it seemed to citrate. He felt the sodium citrate was practically the enhance the retarding action of the bromide. only control they possessed. When the plate was over-exposed, the results were as Mr. Watkins had The CHAIRMAN said Mr. Chapman Jones had

dealt with much that he had intended touching upon.

Everyone must admire the great care with which Mr. Rev. F. C. LAMBERT said he felt the following | Watkins had conducted and recorded his experiments difficulty. If he had a slow plate giving a considerable on development, and that gentleman bad cast a new range of exposure, was he to understand that one had light on many manipulations in that process. Mr. to take the time from the pouring on of the developer Watkins had shown that there was a factor, which, if to its first appearance, and multiply that for a constant used, would enable the photographer always to arrive factor under all conditions ? Suppose the image ap at the same degree or intensity of gradation. Of peared in ten seconds, and the factor was six, he course there was a certain difficulty in arriving at a must develop for one minute; if with that plate he factor. For instance, what was the first appearance ? gave the shortest possible exposure, and gave the That was to a large extent a question of a personal other half of the plate the longest possible exposure, equation, and with that be fully agreed. One person he would expect under those conditions that the time would see a black speck coming out on a negative of the appearance of the image would be different; the before another person. He had often developed more brief the exposure the slower would be the pic. side by side with his assistants and friends, and it had ture in appearing; but if he used the saine factor in often been difficult to decide at what exact time the both cases, would he get the same result ? He anti image appeared. But that could be got over, and cipated an opposite result, because be imagined that wben once the personal equation had been arrived at, for the same degree of contrast, the longer exposure, one could have a factor for different kinds of plates which came out first, should have the higher multi for development. He had made a great many experi. plying factor.

ments, and he had come to the conclusion that there was

a great deal more control in developing a negative Mr. W. THOMAS, speaking as an oruinary prac- than Mr. Watkins liked to allow. He was not a protical photographer, said that what one wanted, as fessional photographer, and therefore he did not a rule, was the maximum result from light action in develop the plates because he was obliged to, but he the shadows, and a very considerable stage of that looked upon the development of every plate as a kind maximum result of light action in higher stages. He of experiment; and if anything remarkable occurred thought highly of the work done by Mr. Watkins, and during the process be repeated it to see what it while agreeing with almost everything he had laid meant. At the time of Hurter and Driffield's paper, down, he could not bring himself to find that his there was a great controversy as to whether there own practice was in accordance with those doctrines. could be an alteration brought about by variation of the Taking a subject with white and as near dark as developer. He had neither the time nor the inclination could be got, some parts lit with clear brilliant sun. | to enter into that controversy; he had a controversy on light and the others in the shade, there was something another point with those same gentlemen, but the to deal with beyond those ; there was such a thing as experiments he had carried out left him no doubt, light and shade, and such a thing as colour. Colour that there was a control in development by means entered into such matters in a very important way. I of varying the developer. On the screen was repreand he thought it was not taken sufficient note of in sented development by means of metol, and one by escriptions and lectures on the subject. It seemed ortol. If one exposed two strips, as be had himself

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