This question of exposure is a most difficult matter upon which to give practical assistance in a handbook. It is true, that by consulting one or other of the many ingenious exposure tables which have been devised the reader with a taste for mathematics may derive some assistance, but those who are not so skilled will probably prefer to dispense with such aid. For my own part, at this early stage of his novitiate, I think their use would tend more to confuse the reader than render him assistance. In ascertaining the correct exposure without resorting to the use of an ex posure table the photographer is naturally compelled to rely mainly upon his judgment ; a quality which the novice lacking the necessary experience obviously cannot be pre sumed to possess. The main factors which guide the photo grapher in correctly estimating exposure are three : the size of the stop, the brightness of the light, and the rapidity of the plate. It should always be borne in mind that the success of the photograph will depend to a great extent upon the accuracy of the exposure; there fore the novice should carefully note the conditions under which he works, so that ho may compare the results obtained one with another. Here the last item on our list of requisites for outdoor work comes to our aid—the ex posure note-book. The pages of this will be found to be ruled off under separate headings, such as " lens," " light," "subject," etc., and these should be filled up after making each exposure, and after the plates have been developed, the results, obtained, whether good, bad, or indifferent, should also be recorded for future guidance.
But after this digression it is time that we exposed our plate. Assuming it to be a bright summer's afternoon, about four o'clock, we remove the cap, and counting " one," " two," quickly replace it. To make sure, as this is our first experiment, we will make a second exposure, this time giving a slightly longer one. We therefore close the shutter, and turn the little wire clip to prevent it being accidentally withdrawn. The dark-slide is then drawn out of the groove in which it fits, and turned over, so that the side with the ivory tablet marked " 2 " is towards the inside of the camera. We now proceed in a precisely similar manner to expose the second plate, the only difference being that in this case we count four seconds instead of two. After we have in the same way exposed a third plate, giving, however, six seconds exposure, we can replace our apparatus and return to the dark-room. Our object in making several exposures upon the same view is to demonstrate, when we come to develop the plates, the effects of under and over-exposure, so that we may obtain as much instruction from our first practical lesson in taking a photograph as possible. Correct exposure will, of course, always be our aim ; but if we err, it should be on the side of over rather than under-exposure—for this reason, that whereas a passable result may, with care, be obtained from an over-exposed negative, nothing can be done with one which is under-exposed.