Timing Development.
Judging by my early experience in the study of photography, I am led to believe that development may be considered the “pons asinorum” of our interesting art science. I had always been more or less unsuccessful in producing respectable negatives by what is termed tentative development, and the papers of Mr. Alfred Watkins of Hereford in the early part of 1894 entitled “A method and instrument for timing development” showed the question to me in quite new light.
It is out of my province in this paper to deal with the subject of correct exposure, and I will merely explain in passing what I believe produces a range of densities having a regular mathematical ratio to each other. Mr Watkins pointed out that in order to secure a correct range of gradation the time the time of development was as important as accuracy in exposure, and whilst it must be borne in mind that his method of timing will not compensate for gross errors in exposure or the use of unsuitable developer, I shall endeavour to demonstrate to you this evening that within reasonable limits of correct exposure (which may be determined by one of the numerous exposure meters or tables on the market) together with one of the commonly known formulae for development , it is possible to produce very satisfactory negatives.
The latitude which may be permitted in exposure varies with the make of plate; I have obtained very good results on some plates with as much as twelve times the normal exposure, while other plates would not yield a suitable negative with more than 8 times the normal exposure.
Having delt with the question of exposure I will now turn to timing, either of the actual development of a plate, and for the purpose of timing, either an ordinary watch (or preferably the Eikronometer invented by Mr. Watkins, which is a small clock and can be more easily seen in the dark room, and which also practically does its own calculating) may be used. The time which elapses between the pouring of the developer and the first appearance of the highlights of the image is carefully noted, and this time multiplied by a suitable factor gives the total time for the development of the plate. I wish here to draw your particular attention to the multiplying factor, which is a variable one, being governed by the class, and in some cases strength of the developer employed, and also upon the density of negative which suits the taste of each individual operator. In the case of Pyro and amidol the multiplying factor varies according to the quantity of each of these agents contained in each ounce of mixed developer; with the other reducing agents, the quantity per ounce does not appear to matter. Again, the quantity of bromide is of importance for if this be increased beyond the normal proportion of say half a grain per ounce, a lower factor must be taken, and this rule holds good for practically all the developing agents, metol excepted.
With regards to the alkali, provided the strength is kept within limits found reasonable in practice and does not cause the time of appearance to be inconveniently short for observation, the actual quantity per ounce of developer does not seem to be of much importance; ammonia is not suitable owing to its quickly loosing strength by evaporation; carbonate of soda or potash, and the caustic alkalis are practically free from the objection and it will be found satisfactory to use one of theses. When Potash is used in conjunction with pyro it appears to have a tendency to produce density a little quicker than when soda is used and a somewhat lower factor is desirable.
The quantity of sulphite, and the temperature of developer if within reasonable limits may also be ignored.
It is worthy of notice that with most of the developers dilution of the mixed solution does not alter the multiplying factor, but as before stated pyro and amidol are exceptions, for any dilution of the developer would reduce the proportion of these salts in each ounce to solution and thereby alter the factor.
I will now give you a list of developers most generally known with their approximate multiplying factors (taken from Mr. Watkins’ book) these times may be modified to suit individual taste, but I have found them to work very well.
PYRO SODA
1 grain per ounce – 11 times the time of appearance
2 grain per ounce – 6 times the time of appearance
3 grain per ounce – 5 ½ times the time of appearance
4 grain per ounce – 4 ½ times the time of appearance
5 grain per ounce – 3 ¼ times the time of appearance
Ilford pyro-soda,
For dense negatives – 5 times the time of appearance
For soft negatives – 6 ½ times the time of appearance
Hydroquinone (with caustic or carbonate of soda) – 5 times the time of appearance
Eikonogen – 9 times the time of appearance
Metol – 23 times the time of appearance
Glycin – 14 times the time of appearance
Amidaol (2 grains per ounce) – 14 times the time of appearance
Rodinal – 40 times the time of appearance
Velox – 12 times the time of appearance
Imperial Pyro-metol – 9 times the time of appearance
Metol & Hydroquinone – 13 times the time of appearance
It will be seen that those developers which are looked upon more particularly as detail givers, and under the influence of which the image appears more quickly, have higher factors, whilst the density givers have longer figures.
As to practical results, I have here a few negatives which have been developed with several of the reducing agents mentioned in the above table, and although I do not claim that they are by any means perfect examples, still, when I tell you that they have all been timed from the first appearance of the highlights and never from the first appearance of the image looked at until fixed, I think you will agree with me that the results are very encouraging and conclusively point to the method being a practical one. Mu arguments in support of it have frequently been pooh-poohed, but the greatest tribute to its worth is the fact that one of my bitterest opponents, and a strong supporter of the tentative school, has been won over, and now times his development.
I have not tried what results can be obtained with lantern slides, but I intend to experiment in this branch and should say that it is possible to obtain more uniform results by timing than it would be by judging the density in the ordinary way.
By the kindness of Mr. Watkins I am able to supplement my own view and portrait negatives with some test slides which have been specially prepared to illustrate the arguments in support of his contention although you will have noticed from the recent developing competition that these arguments do not appear to hold good in the case of a developer containing a very heavy proportion of pyro.
A word or two in regard to exposure meters or tables; I do not agree with those who oppose the use of these aids, as I think that most of them, especially those on the actinometer principle are of great assistance in judging exposure, and I cannot believe that it is possible to arrive at a correct estimate by the judgment alone. I can safely say that my percentage of failures since I used these aids and timed my development has dwindled down to an insignificant amount compared with what they used to be, and my inferior results must now be attributed to carelessness in manipulation , accidental fog, uncertain hand-camera exposure etc. You will notice that even the snap shots which I will pass round have turned out exceedingly well considering that some of them were taken in the height of summer and others in the middle of October, all about the same time of day with the same stop and same speed of shutter.”