By J. STERRY,
Honorary Fellow of the Royal Photographic Society.
As the first catalogue of Bromide Papers, taken at random, gives eighteen varieties from which to make a choice, the beginner may need some help in his first selection. There need not be much trouble, however, as all may be readily classified thus : -
J. Sterry, F.R.P.S.
Surface. - Glossy, Smooth, Rough, Matte. Colour. - White, Mauve, Pink, Tinted. Rapidity. - Rapid, Slow, Very Slow. Gradation. - Long, Medium, Short.
It will be seen that the most important differences are in the rapidity and gradation, whilst surface and colour may be looked upon as varieties only, which later on will be selected specially to suit the subject in hand.
But little, also, need be said respecting rapidity, as that simply governs the relative duration of the exposure with any given negative, whilst, of course, in the case of rapid papers greater care must be taken to prevent the action of stray light during the different processes. The various uses for different rapidities may be classified thus : TABLE II. Rapid. - For enlarging by artificial light and the contact printing of dense negatives.
Slow. - For enlarging by daylight or contact printing of negatives of medium density.
Very Slow. - (Gaslight papers) are specially suited to the contact printing of negatives which are very thin and weak.
The rapid and slow require the use of a dark-room, but a bright orange light is all that is needed for safety in working. The gaslight papers have the further advantage of being readily worked in a room lighted by gas.
It is here that the greatest difference in the character of various papers will be found, and for want of a knowledge of which the beginner often meets with failure in his bromide printing. Not being able to attribute his troubles to the real cause, he is unable to determine as to whether it is his own fault in working or the unsuitability of the paper to the negative from which he wishes to print.
But very little information is given by the makers upon this point, notwithstanding its great importance, therefore, before dealing with practical working, it will be well to try and make it as clear as possible. When once thoroughly understood and working upon the lines to be laid down, it will be quite easy to determine what can and what cannot be done with any given paper or negative.
Gradation may be described as the range of the paper, or its power to represent varied degrees or proportions of light action.
The shortest gradation or range found in any paper is about 1 to 16, that is, if an exposure of one second to the chosen source of light at a specified distance just gives the faintest possible trace of action upon the paper, when fully developed, then about sixteen seconds at the same distance would be found to give the deepest black obtainable.
On the other hand, a very long range paper would probably be found to require over one hundred times as much exposure to obtain the deepest shade as would be needed just to impress it at all, the development being in this case also carried as far as possible.
Seeing that any negative selected for trial must transmit a definite scale of light intensities according to the density of the silver deposits, it is clear that the same result could not possibly be obtained on both papers (short and long range) if the development were carried out to the full.
Now, whilst it is true that stopping the development before it is quite completed does somewhat alter the scale, the control thus obtained is so slight, that the better plan is to ignore it altogether and start with the general rule, that development shall be carried to the full. Any slight disadvantage due to this determination is amply compensated for in the certainty of being able to duplicate results, and also in the ease and speed of working generally. (Later on, a slight chemical modification in the development will be described which gives a real change in the gradation of the paper at will).
The object of this paper is to give the best plan of working for a difficult subject, requiring the fullest range of white to black that can be obtained, such as a landscape with bright clouds and deep shadows. More easy subjects not using the full scale of light will not receive special consideration, upon the principle that " the greater includes the less." Very poor results are often seen in bromide prints because so many think that any negative and any paper should somehow be made to work together, which is very far from being the case.
From what has been said about gradation it is evident that there must be some particular character in the negative which will make it suitable for printing with each of the papers. This difference is found to be solely connected with the development of the plate, and has nothing whatever to do with the exposure in the camera. Given correct exposure, then the relative duration of development solely determines the printing character of the negative and its suitability for obtaining the best results by different printing processes.
For bromide printing generally, and especially for enlarging, the negative requires less development than for any other printing process.
The following table will give a general idea of the differences needed in the development of the negative to make it best suited to the different papers.
Development of the Negative.
Character of the Negative.
Paper for Contact Printing.
Paper for Enlarging.
Rapid brom. and special treatment.
Do. and special treatment.
Unless one is specially preparing negatives for bromide printing, it is better generally to develop, so that they will be of use for another process such as platinum printing, and then to classify them according to the table above. It will then be possible to select the most suitable paper or mode of working.