The amatuer photographer who on the score of expense or because of its greater portability elects to purchase a small camera rather than a large one, will always have the satisfaction of reflecting that his small pictures can be enlarged. The image afforded by the camera is so perfect in its details that (unless this enlargement be carried to an extravagant extent) it suffers no harm by being greatly magnified. As a proof of this we may point to the ordinary photographic lantern slide, the visible part of which measures less than three inches in diameter. Yet such tiny pictures are constantly used by professional lecturers, who think nothing of showing them enlarged by the limelight on a screen measuring 15 to 18 feet across. We give this as an instance of the perfection of detail which a good photograph is capable of affording. The amateur will be content if he can enlage his quarter plates, or 5 x 4 negatives to 12 x 10 or 15 x 12 We would not advise him to attempt any larger size than the latter, at any rate, until he has had some experience of this branch of photographic work.
Before proceeding to enlarge a negative the operator must consider one important point. Does he want one or two copies of the enlarged picture, or does he require a dozen or more? In the first case he will seek to produce enlarged positives direct on paper. In the latter case his best plan will be to obtain an enlarged negative from which as many prints can be obtained as he may require by the ordinary method with the printing frame. The negative may be a paper one if preferred, for paper admirably adapted to this purpose can now be obtained.
There are many different methods by which an enlarged picture can be obtained. Many of these require an extensive plant such as amateur workers would never think of purchasing. A few years ago such work would not be attempted except by experienced professional photographers, but since the introduction, about five years back, of a special kind of paper called "gelatino-bromide" paper, the operation of enlarging has been so much simplified that it now presents no great difficulty. The paper mentioned is in every respect similar to a gelatine plate, except that the sensitive emulsion of bromide of silver, instead of being supported on glass, is spread upon paper. It is sold in light tight boxes, at a cheap rate, and in dealing with it all the precautions against access of white light which are necessary in working gelatine plates must be observed.
The simplest and cheapest method of enlarging is to use daylight as the illuminator, and the following method may be recommended. Choose a window, if possible, from which there is an uninterrupted view of the sky. Carefully close it all up with brown paper, except a space sufficiently large to contain a printing frame holding the negative to be enlarged. The frame must be without its back and with the springs removed from it. The negative can be supported in it by tacks, and the film side should be placed inwards towards the room. This frame can be easily supported in position at a convenient height by strips of wood, one above and one below, screwed at each end into the window frame. To the lower strip also attach a shelf large enough to hold a camera. The camera is placed on this shelf with its lens pointing away from the window.
Having arranged these details, it will be found that an enlarged image of the negative will be cast upon a sheet of cardboard held a few feet from the camera, the size of the picture depending upon the distance. By moving the camera to and fro on its shelf, which should be long enough to give a little play in this respect, the image can easily be sharply focussed.
Now place on a table a box or board which can act as a solid screen for the reception of the image. It must be firm, whatever else it be. Cover it with white paper or tack a sheet of cardboard upon it. This is your focussing screen. Mark out upon it a space 15 x 12, or any other size that you may determine upon, and move it and the camera until the image fills the space. Take a strip of the gelatino bromide paper, 2 or 3 inches wide and 12 inches long, and after covering the negative in the window with a piece of card so as to shut off the light, pin this strip to your screen. Place in front of it a piece of orange paper which will cover three-quarters of it, so that when you uncover the negative and allow the light to do its work only one-quarter of the paper strip will be affected. Now expose for, say 5 minutes. Cover the negative, and uncover another quarter of the strip, and expose once more for 5 minutes. Do this the third time with another quarter, and once more with the whole strip exposed to the light coming through the negative. As a result you have a trial strip of paper the four parts of which have received exposures respectively of 5, 10, 15, and 20 minutes. Develope this strip, and it will be an unfailing guide to the amount of density obtainable with a negative of a certain quality and under certain conditions of light. The experiment may seem a tedious one, but it is worth the trouble, and will perhaps save many a sheet of sensitive paper which would otherwise be sacrificed in trial exposures.
As to development, we need not describe it here, because copious directions accompany, each packet of paper. We may merely remark that the method employed is the ferrous oxalate formula already given, but it is modified in one or two details.