" Now you see there is no danger of tripping over that leg or upsetting the camera while you are arranging the focus; also you will see that to raise the front of the camera or lower the back in order to level it, you simply use the forward leg as a sort of pivot while you raise the others from the ground, taking one in each hand, near the upper part." Finally he succeeds in getting 'his focus, which he obtains by moving the front part of the camera, which bears the lens, back or forward until the picture shows with distinctness upon the ground-glass. Still he is not satisfied. He has his focus all right, but he finds that he is not able to see the top of the steeple. He is trying to take this picture of a high building across the narrow side of his plate. Now his is a reversible swing-back camera, and his 5x8 plate is placed horizontally in the camera, so we reverse the ground-glass by turning it one-fourth around which makes it stand perpendicular to its former position. This allows him to see on the ground-glass more of the steeple than he could before, but still the top is not in view. We notice that the front of the camera, which carries the lens, moves up and down. We, therefore, loosen the thumb-screw and raise the front, and with it the lens, and we find on looking again at the picture on the ground-glass, that we have now the whole of the church in view. Raising this front has cut'off some of the fore ground, which we did not need, and has enabled us to take in the extreme top of the steeple. We could, however, have accom plished this result in a different way. Instead of raising the front, which we now replace, we set back the forward leg of the tripod, which has the effect of tilting the camera up, and on look ing at the ground-glass again we find that by pointing the camera up we take in the whole of the church steeple as we did before; but we notice, however, another queer thing. The sides of the church, instead of being perpendicular as they should be, seem to lean inward as if they would come to a point if ex tended. Of course, this would give us an absurd representation of the building if we should photograph it in that way, and to correct this we have recourse to the swing-back of the camera. When we tilted the camera, we noticed that the ground-glass, which before had been perpendicular, was inclined backward. We loosen the thumb-screw which holds the swing-back and in cline the upper part of the back forward, keeping our eyes on the picture on the ground-glass as we do this. As the glass is in clined forward we notice that the perpendicular lines of the building gradually become erect, and when they seem to be per fectly true and parallel to each other we tighten the thumb-screw to hold the back in that position. We notice now in looking at the back of the camera that, while the forward part of the camera is tilted up, the back of the camera carrying the ground glass is perpendicular. . We make a note of this, which we shall find afterwards of great use in taking other photographs of buildings or in copying pictures; that is, that for such work the ground glass, which occupies the place of the plate, should he parallel to the surface which we wish to copy. This is one of the uses of the swing-back of the camera; other uses of that as well as of the side-swing we shall refer to later.
We have now to decide upon the stop or diaphragm to use in the lens. We will not here discuss the different uses of the stops, leaving that for a subsequent chapter, and will select a stop which is marked f 32, which in this case, as the focus of the lens is eight inches, is a stop measuring a quarter of an inch in diameter. We insert the stop, put the cap upon the lens and the plate-holder in its place all ready to draw the slide and make the exposure. Before making the real exposure, however, we shall practice a little on counting the time and on taking off the cap.
" Now will each one of you please take off the cap and count the time, and at the end of the time replace the cap as neatly and carefully as you can. We will say that the time that we are going to give to the exposure is six seconds. Now let the first one try." " Well, you made the mistakes that are usually made in these operations. You removed the cap gently, which was all right, but after you had taken it from the lens you held it for nearly a second directly in front of the lens and then gradually lowered it. Of course, while the cap was in front of the lens it obscured so much of the landscape and delayed the exposure. Again, your time instead of being six seconds was only three seconds. Now let the next boy try." " That was a little better in one respect and worse in another. You came nearer to the time, your exposure was five seconds, but you were too hasty in removing the cap and you shook the camera perceptibly. Now if the building of which you were taking a picture should shake a little like that it would not make much difference, as long as it did not shake the plate. But when you shake the camera, and with it the plate, that blurs the picture on the plate beyond redemption. We will now let the other boy try and see how well he performs these two operations." " That was very much better; the cap was taken off gently but firmly, and as soon as removed it was brought down out of sight without jarring the camera in the slightest. But you have counted your time too slow, and instead of six seconds you have made it twelve seconds. Two of you counted the time and one of you guessed, and none of you were right. Of course, you could use a watch with which to count your time, but you would not always get it exact in that way, especially if you wanted one or two sec onds, as part of the time would go by after you removed the cap until you could notice the face of your watch. We have, how ever, one very reliable way of counting seconds or parts of seconds. Suppose we wanted six seconds. We commence to say the mo ment the cap is off the lens, one-thousand one, one-thousand two, one-thousand three, one-thousand four, one-thousand five, one-thousand six.' Just as we say the six we replace the cap on the lens. Suppose we wanted two and one-half seconds, then we would say, ' one-thousand one, one-thousand two, one-thou'— and cap the lens. Counting in that way, you will have no diffi culty in counting any time from one-half second to a minute. It is something you need to remember." " Now we are all ready to take the picture, and we lay the focusing cloth over the camera so that it covers every thing but the lens; we draw the slide, the front slide of our plate-holder, removing it entirely from the holder, keeping the camera at the same time covered with the focusing cloth. Then we look to see that the camera is perfectly still, and, removing the cap, count our time, and the exposure is made; the cap being replaced at the end of the time. Now remember about the slide of the plate holder when we replace it, we must have the dark side out, which will show us that there is an exposed plate in that side of the plate holder ; also when we put it in the holder we must be careful to put it in squarely, not one corner at a time, but to put it in so that the whole end of the slide will at the same time enter the slit of the holder. If not done in this way, light will be likely to get in the holder and fog the plate. When we get back to our dark-room and have emptied a plate-holder you can hold one of them up to the light and see how the insertion of one corner of the slide in the slit opens the shutter along the whole width so that you can see the light plainly through it." Our young friend here removes the plate-holder which he places carefully in the box holding the others, and proceeds with his camera to walk on and take other views.