A rapid rectilinear is the best lens to employ, though if the reader does not possess one, any other kind may be used—single, wide-angle, or portrait. He will generally be safe in using the lens with which the negative was taken, and if he has but one lens, and the advice previously given has been followed, that will be a rapid rectilinear.
The manner in which the apparatus is to be used is sufficiently obvious. The apparatus having been set up, the actual procedure is very simple. The negative to be enlarged is placed in the rebated groove, and the buttons turned to prevent it from falling out. The lens and camera being placed in position, the enlarged image will then fall upon the drawing-board. Its size, as I have already pointed out, will be determined by the distance at which the lens is placed from the negative. In the Dictionary of Ph,otography will be found a very useful table giving the distances at which the lens should be placed from the negative for lenses of different focal length ; a reference to which will save much trouble in effecting the rough adjustment. The final focussing of the enlarged image is effected either by moving the pinion of the camera, or by shifting the drawing-board backwards and forwards until the image is quite sharp. If the lens be a good one there should be no necessity to stop it down to any considerable extent ; f/16 should be quite sufficient, and it must be recollected that stopping down will considerably increase the duration of the exposure. The image having been sharply focussed and the lens capped, a piece of bromide paper is removed from its packet and secured to the drawing-board by means of drawing-pins. The exposure may now be given, but its duration will depend upon a variety of circumstances—the density of the negative, the strength of the light, the aperture of the lens, the rapidity of the bromide paper, and a variety of other factors, all of which must be ascertained before any reliable advice can be given. The easiest and most practical way of finding out the correct exposure, although it is only a " rule-of thumb " method, is to cut up one of the pieces of bromide paper into twelve strips, pin one of these on the centre of the drawing-board, covering all but three-qua,rters of it with a piece of card, now uncap the lens and give an exposure of say ten seconds; recap the lens, push the card so that it covers half the paper, and give another five seconds ex posure ; repeat the operation a third and a fourth time, so that the strip of paper will have received four different ex posures. It should then be developed, when its behaviour
will soon determine which exposure was most correct.
In regard to development little need be said, for the in structions given in the preceding chapter on bromide print ing apply equally to the development of enlargements. The reader should implicitly follow the directions for the mixing of the solutions, etc., as the modified developer recommended will be found easier to xnanage, and will give better results than the strong solutions usually employed.
A good and sharp negative will bear enlarging several diameters without any very perceptible loss of definition, but a negative which is wanting in sharpness will not give a good enlargement, Soft 0,nd rather thin negatives are the best for enlarging; dense ones do not enlarge well. There fore if the negatives are intended for enlarging, some atten tion should be paid to these matters at the time of exposure and during development, so that a suitable negative may be obtained.
Sometimes it is not possible to secure a room with a window facing north, and the view from which is not obstructed. In such a case it will be necessary to use a reflector. This need not be a mirror, which would be costly, but may be made of thin boards neatly joined, and painted with a dull white paint. It should be fitted outside the window at an angle of 45° with the negative. Working with a reflector obviates any difficulty with objects opposite the window, such as houses, trees, etc., only reflected light from the sky being utilised.