32 Cincinnati Society of Natural History. 



LANTERN SLIDES. 



By E. J. Carpenter. 



(Read at meeting of the Photographic Section May 6, 1886.) 



There is probably no other way in wnich a photographer can 

 so satisfactorily show the results of his work as by projecting the 

 views on the screen by means of the so-called magic lantern, and I 

 find in my own experience that many who do not care for or appre- 

 ciate the best results presented in the form of silver prints on paper 

 are pleased and interested by the same views when shown on the 

 screen. This is no doubt mainly due to the increased size of the 

 pictures, which gives them a reality so vivid that it is not difficult 

 to imagine that the spectator might, if so inclined, step out into 

 the scene presented before him, and I have known children to 

 voluntarily speak to friends whom they recognized, and whose 

 presence seemed so real when presented in this manner. 



Fortunately, the production of pictures for use with the lan- 

 tern is now one of the easiest and simplest of photographic opera- 

 tions. Any negative that will make a passable silver print may 

 be used, and in addition many are available, which by reason of 

 various imperfections cannot be used at all for ordinary printing. 

 The operation is, briefly, to make a transparent positive on glass 

 of the proper size, usually 3^x4 inches. 



The tests of a first rate lantern slide are as follows : The 

 image must be clear and brilliant, having contrast without harsh- 

 ness. The highest lights should be clear glass without a trace of 

 silver deposit; and the deepest shadows should be sufficiently 

 transparent to permit all detail to be seen. When the plate is laid 

 on a white printed sheet the type should be legible through the 

 shadows, and the lights should show no deposit. 



The easiest method of making positives is to print by contact 

 in the pressure frame just as is done in silver printing, but for this 

 purpose it is necessary that the negatives should be of the proper 

 size, which is not usually the case unless they happen to have been 

 made specially for the purpose. I have often made contact posi- 

 tives, but only where I wished to use a small portion of a larger 

 negative, or when the slides were to be made by copying photo- 

 graphs or engravings. In the latter case a small negative is made 

 of the copy, usually on a 4x5 plate, which size is large enough 

 to enable one to properly adjust the plate on which the positive is 

 to be made. 



