Lantern Slides. 33 



If the negative to be copied is larger than the required posi- 

 tive, recourse is had to the camera. The negative is set up in a 

 frame, and the camera is placed facing it in such a manner that 

 the ground glass is parallel to and opposite the center of the nega- 

 tive. It is then moved back or forward until the image of the 

 negative is of the proper size when focused. The operation of 

 focusing is one requiring the greatest care, and is also one which 

 does not, I am afraid, receive the attention its importance de- . 

 mands. Very few people have eyesight sufficiently sharp to en- 

 able them to perform this operation without the aid of a magnify- 

 ing glass, and to those who think they have I would suggest to try 

 the experiment of examining carefully with an ordinary hand mi- 

 croscope any lantern slides made without the use of such a glass to 

 focus the image. The result will probably surprise them, as I will 

 confess it did me when I compared in this way Iwo sets of slides 

 made from the same negatives, one lot made by using the glass to 

 focus, and the other by unassisted, but rather more than usually 

 keen, eyes. Among the most common faults of the various slides 

 submitted for criticism has been this of poor focussing when mak- 

 ing the copy. When it is remembered that the operation of once 

 focussing will suffice for probably all the positives to be made dur- 

 ing an afternoon or a day, it will be seen that the little time re- 

 quired to do it perfectly is well spent. 



The best apparatus and the easiest to use for reducing nega- 

 tives and making slides is the co|)ying camera, a good specimen of 

 which belongs to this Society. Before making the exposure, if an 

 ordinary camera be used, it is necessary to cover over the space 

 between the lens and the negative to be copied, so as to prevent 

 any light from reaching the lens that does not pass through the 

 negative. If this is not done a brilliant positive will not be ob- 

 tained, because a certain amount of this extraneous light will be 

 distributed over the sensitive plate, and cause a veiling of the high 

 lights, which ought to be perfectly clear. 



If a portrait lens be used in the copying camera, and this 

 form of lens gives most satisfactory results, it will be necessary to 

 stop it down considerably, though even then it will be found that 

 the exposures are shorter than with any of the various view or 

 group lenses. As most lantern slides are made in the winter 

 season when the light is weak, and clouds, smoke, etc., still 

 further impair its activity, it is a matter of some importance to 

 have a quick-working lens. 



